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Guillermo bought textbooks and notebooks at the bookstore. The number of textbooks was 3 more than the number of notebooks. He bought 5 textbooks. How many notebooks did he buy?

2

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Gerry worked Sudoku puzzles and crossword puzzles this week. The number of Sudoku puzzles he completed is seven more than the number of crossword puzzles. He completed 14 Sudoku puzzles. How many crossword puzzles did he complete?

7

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In Solve Sales Tax, Commission, and Discount Applications , we learned how to translate and solve basic percent equations and used them to solve sales tax and commission applications. In the next example, we will apply our Problem Solving Strategy to more applications of percent.

Nga's car insurance premium increased by $60 , which was 8% of the original cost. What was the original cost of the premium?

Solution

Step 1. Read the problem. Remember, if there are words you don't understand, look them up.
Step 2. Identify what you are looking for. the original cost of the premium
Step 3. Name. Choose a variable to represent the original cost of premium. Let c = the original cost
Step 4. Translate. Restate as one sentence. Translate into an equation.
.
Step 5. Solve the equation. .
Divide both sides by 0.08. .
Simplify. c = 750
Step 6. Check: Is our answer reasonable? Yes, a $750 premium on auto insurance is reasonable. Now let's check our algebra. Is 8% of 750 equal to 60?
.
.
.
Step 7. Answer the question. The original cost of Nga's premium was $750.
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Pilar's rent increased by 4% . The increase was $38 . What was the original amount of Pilar's rent?

$950

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Steve saves 12% of his paycheck each month. If he saved $504 last month, how much was his paycheck?

$4,200

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Solve number problems

Now we will translate and solve number problems . In number problems, you are given some clues about one or more numbers, and you use these clues to build an equation. Number problems don't usually arise on an everyday basis, but they provide a good introduction to practicing the Problem Solving Strategy . Remember to look for clue words such as difference , of , and and .

The difference of a number and six is 13 . Find the number.

Solution

Step 1. Read the problem. Do you understand all the words?
Step 2. Identify what you are looking for. the number
Step 3. Name. Choose a variable to represent the number. Let n = the number
Step 4. Translate. Restate as one sentence.
Translate into an equation.
.
Step 5. Solve the equation.
Add 6 to both sides.
Simplify.
.
.
.
Step 6. Check:
The difference of 19 and 6 is 13. It checks.
Step 7. Answer the question. The number is 19.
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The difference of a number and eight is 17 . Find the number.

25

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The difference of a number and eleven is −7 . Find the number.

4

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The sum of twice a number and seven is 15 . Find the number.

Solution

Step 1. Read the problem.
Step 2. Identify what you are looking for. the number
Step 3. Name. Choose a variable to represent the number. Let n = the number
Step 4. Translate. Restate the problem as one sentence.
Translate into an equation.
.
Step 5. Solve the equation. .
Subtract 7 from each side and simplify. .
Divide each side by 2 and simplify. .
Step 6. Check: is the sum of twice 4 and 7 equal to 15?
.
.
.
Step 7. Answer the question. The number is 4.
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Source:  OpenStax, Prealgebra. OpenStax CNX. Jul 15, 2016 Download for free at http://legacy.cnx.org/content/col11756/1.9
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