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Kenneth currently sells suits for company A at a salary of $22,000 plus a $10 commission for each suit sold. Company B offers him a position with a salary of $28,000 plus a $4 commission for each suit sold. How many suits would Kenneth need to sell for the options to be equal?

Kenneth would need to sell 1,000 suits.

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Access these online resources for additional instruction and practice with solving systems of equations by substitution.

Key concepts

  • Solve a system of equations by substitution
    1. Solve one of the equations for either variable.
    2. Substitute the expression from Step 1 into the other equation.
    3. Solve the resulting equation.
    4. Substitute the solution in Step 3 into one of the original equations to find the other variable.
    5. Write the solution as an ordered pair.
    6. Check that the ordered pair is a solution to both original equations.

Practice makes perfect

Solve a System of Equations by Substitution

In the following exercises, solve the systems of equations by substitution.

{ 2 x + y = −4 3 x 2 y = −6

( −2 , 0 )

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{ 2 x + y = −2 3 x y = 7

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{ x 2 y = −5 2 x 3 y = −4

( 7 , 6 )

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{ x 3 y = −9 2 x + 5 y = 4

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{ 5 x 2 y = −6 y = 3 x + 3

( 0 , 3 )

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{ −2 x + 2 y = 6 y = −3 x + 1

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{ 2 x + 3 y = 3 y = x + 3

( 6 , −3 )

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{ 2 x + 5 y = −14 y = −2 x + 2

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{ 2 x + 5 y = 1 y = 1 3 x 2

( 3 , −1 )

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{ 3 x + 4 y = 1 y = 2 5 x + 2

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{ 3 x 2 y = 6 y = 2 3 x + 2

( 6 , 6 )

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{ −3 x 5 y = 3 y = 1 2 x 5

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{ 2 x + y = 10 x + y = −5

( 5 , 0 )

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{ −2 x + y = 10 x + 2 y = 16

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{ 3 x + y = 1 −4 x + y = 15

( −2 , 7 )

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{ x + y = 0 2 x + 3 y = −4

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{ x + 3 y = 1 3 x + 5 y = −5

( −5 , 2 )

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{ x + 2 y = −1 2 x + 3 y = 1

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{ 2 x + y = 5 x 2 y = −15

( −1 , 7 )

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{ 4 x + y = 10 x 2 y = −20

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{ y = −2 x 1 y = 1 3 x + 4

( −3 , 5 )

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{ y = x 6 y = 3 2 x + 4

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{ y = 2 x 8 y = 3 5 x + 6

(10, 12)

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{ y = x 1 y = x + 7

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{ 4 x + 2 y = 8 8 x y = 1

( 1 2 , 3 )

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{ x 12 y = −1 2 x 8 y = −6

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{ 15 x + 2 y = 6 −5 x + 2 y = −4

( 1 2 , 3 4 )

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{ 2 x 15 y = 7 12 x + 2 y = −4

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{ y = 3 x 6 x 2 y = 0

Infinitely many solutions

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{ x = 2 y 4 x 8 y = 0

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{ 2 x + 16 y = 8 x 8 y = −4

Infinitely many solutions

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{ 15 x + 4 y = 6 −30 x 8 y = −12

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{ y = −4 x 4 x + y = 1

No solution

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{ y = 1 4 x x + 4 y = 8

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{ y = 7 8 x + 4 −7 x + 8 y = 6

No solution

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{ y = 2 3 x + 5 2 x + 3 y = 11

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Solve Applications of Systems of Equations by Substitution

In the following exercises, translate to a system of equations and solve.

The sum of two numbers is 15. One number is 3 less than the other. Find the numbers.

The numbers are 13 and 17.

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The sum of two numbers is 30. One number is 4 less than the other. Find the numbers.

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The sum of two numbers is −26. One number is 12 less than the other. Find the numbers.

The numbers are −7 and −19.

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The perimeter of a rectangle is 50. The length is 5 more than the width. Find the length and width.

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The perimeter of a rectangle is 60. The length is 10 more than the width. Find the length and width.

The length is 20 and the width is 10.

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The perimeter of a rectangle is 58. The length is 5 more than three times the width. Find the length and width.

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The perimeter of a rectangle is 84. The length is 10 more than three times the width. Find the length and width.

The length is 34 and the width is 8.

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The measure of one of the small angles of a right triangle is 14 more than 3 times the measure of the other small angle. Find the measure of both angles.

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The measure of one of the small angles of a right triangle is 26 more than 3 times the measure of the other small angle. Find the measure of both angles.

The measures are 16° and 74°.

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The measure of one of the small angles of a right triangle is 15 less than twice the measure of the other small angle. Find the measure of both angles.

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The measure of one of the small angles of a right triangle is 45 less than twice the measure of the other small angle. Find the measure of both angles.

The measures are 45° and 45°.

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Maxim has been offered positions by two car dealers. The first company pays a salary of $10,000 plus a commission of $1,000 for each car sold. The second pays a salary of $20,000 plus a commission of $500 for each car sold. How many cars would need to be sold to make the total pay the same?

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Jackie has been offered positions by two cable companies. The first company pays a salary of $ 14,000 plus a commission of $100 for each cable package sold. The second pays a salary of $20,000 plus a commission of $25 for each cable package sold. How many cable packages would need to be sold to make the total pay the same?

80 cable packages would need to be sold.

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Amara currently sells televisions for company A at a salary of $17,000 plus a $100 commission for each television she sells. Company B offers her a position with a salary of $29,000 plus a $20 commission for each television she sells. How televisions would Amara need to sell for the options to be equal?

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Mitchell currently sells stoves for company A at a salary of $12,000 plus a $150 commission for each stove he sells. Company B offers him a position with a salary of $24,000 plus a $50 commission for each stove he sells. How many stoves would Mitchell need to sell for the options to be equal?

Mitchell would need to sell 120 stoves.

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Everyday math

When Gloria spent 15 minutes on the elliptical trainer and then did circuit training for 30 minutes, her fitness app says she burned 435 calories. When she spent 30 minutes on the elliptical trainer and 40 minutes circuit training she burned 690 calories. Solve the system { 15 e + 30 c = 435 30 e + 40 c = 690 for e , the number of calories she burns for each minute on the elliptical trainer, and c , the number of calories she burns for each minute of circuit training.

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Stephanie left Riverside, California, driving her motorhome north on Interstate 15 towards Salt Lake City at a speed of 56 miles per hour. Half an hour later, Tina left Riverside in her car on the same route as Stephanie, driving 70 miles per hour. Solve the system { 56 s = 70 t s = t + 1 2 .

  1. for t to find out how long it will take Tina to catch up to Stephanie.
  2. what is the value of s , the number of hours Stephanie will have driven before Tina catches up to her?

t = 2 hours s = 2 1 2 hours

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Writing exercises

Solve the system of equations
{ x + y = 10 x y = 6

by graphing.
by substitution.
Which method do you prefer? Why?

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Solve the system of equations
{ 3 x + y = 12 x = y 8 by substitution and explain all your steps in words.

Answers will vary.

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Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This figure shows a table with three rows and four columns. The columns are labeled, “I can…,” “Confidently.” “With some help.” and “No - I don’t get it.” The only column with filled in cells below it is labeled “I can…” It reads, “solve a system of equations by substitution.” “solve applications of systems of equations by substitution.”

After reviewing this checklist, what will you do to become confident for all objectives?

Questions & Answers

differentiate between demand and supply giving examples
Lambiv Reply
differentiated between demand and supply using examples
Lambiv
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Lambiv
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appreciation
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In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
Ezea
What is ceteris paribus?
Shukri Reply
other things being equal
AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
Kelo
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Shukri
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Shukri
what is monopoly mean?
Habtamu Reply
What is different between quantity demand and demand?
Shukri Reply
Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
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Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
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Jabir
What do you think is more important to focus on when considering inequality ?
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sir...I just want to ask one question... Define the term contract curve? if you are free please help me to find this answer 🙏
Asui
it is a curve that we get after connecting the pareto optimal combinations of two consumers after their mutually beneficial trade offs
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In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
Feyisa Reply
Answer
Feyisa
c
Jabir
the market for lemon has 10 potential consumers, each having an individual demand curve p=101-10Qi, where p is price in dollar's per cup and Qi is the number of cups demanded per week by the i th consumer.Find the market demand curve using algebra. Draw an individual demand curve and the market dema
Gsbwnw Reply
suppose the production function is given by ( L, K)=L¼K¾.assuming capital is fixed find APL and MPL. consider the following short run production function:Q=6L²-0.4L³ a) find the value of L that maximizes output b)find the value of L that maximizes marginal product
Abdureman
types of unemployment
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What is the difference between perfect competition and monopolistic competition?
Mohammed
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Source:  OpenStax, Elementary algebra. OpenStax CNX. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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