Elementary Algebra

Published by Cengage Learning
ISBN 10: 1285194055
ISBN 13: 978-1-28519-405-9

Chapter 3 - Equations and Problem Solving - 3.3 - More on Solving Equations and Problem Solving - Problem Set 3.3: 65

Answer

The cost of the biology book is 91 dollars.

Work Step by Step

Let X represent the cost of a used textbook for college algebra. Twice the cost of a used textbook for college algebra means 2X. 15 more than twice the cost of a used textbook for college algebra means 2X + 15. Since the cost of the two books together is 129, we can set up the following equation: 2X + 15 + X = 129. 3X + 15 = 129 Subtract 15 from both sides 3X = 114 Divide both sides by 3 X = 38 Since the cost of the biology book is 2X + 15, and X = 38, the cost of the biology book is 91 dollars.
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