Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter 4 - Section 4.4 - Systems of Linear Equations and Problem Solving - Exercise Set: 18

Answer

A DVD is 15 dollars. A CD is 7 dollars.

Work Step by Step

Let $D$ be the price of a DVD. Let $C$ be the price of a CD. Two DVDs and five CDs for 65 dollars. $2D+5C=65$ Four DVDs and three CDs for 81 dollars. $4D+3C=81$ $2D+5C=65$ $4D+3C=81$ Multiply first equation by -2. $-4D-10C=-130$ $4D+3C=81$ Add both equations. $-7C=-49$ $C=7$ Solve for $D$ $2D+5C=65$ $2D+5(7)=65$ $2D+35=65$ $2D=30$ $D=15$ A DVD is 15 dollars. A CD is 7 dollars.
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