# Solving a Percent Equation on the ISEE

#### Middle and Upper Level

**ISEE Question:** A book is on sale for 20% off. The discounted price of the book is $18. What was the original price before the discount?

**Solution:** Write and then solve a percent equation that matches the word problem.

**STEP 1:** Identify/underline the key numbers and circle or underline what the question is asking.

A book is on sale for __20% off__. The discounted price of the book is __$18__. __What was the original price before the discount?__

**STEP 2:** Convert the word problem into an equation. Convert percents into fractions or decimals. “Of” means “multiply” and “is” means “equal.” Use a variable for your unknown value.

Let *b* = original price*b* – 0.2*b* = 18

0.8*b* = 18

**Helpful tip:** If you’re finding a discount, you must subtract the percent of the discount multiplied by the original price. (You can often do this step mentally.) Do not write *b* − 0.2 = 18. This will only subtract 20 cents, not 20% of the price!

**STEP 3:** Solve the equation.

The original price of the book was $22.50.