Algebra 1

Published by Prentice Hall
ISBN 10: 0133500403
ISBN 13: 978-0-13350-040-0

Chapter 6 - Systems of Equations and Inequalities - 6-3 Solving Systems Using Elimination - Practice and Problem-Solving Exercises: 20

Answer

(4,7)

Work Step by Step

Multiply the first equation by 8. Multiply the second equation by 9. Add the two equations to eliminate y. $5x-9y=-43\ \ \ \ $multiply by 8$\ \ \ \ 40x-72y=-344$ $3x+8y=\ \ \ 68\ \ \ \ $multiply by 9$\ \ \ \ \underline{27x+72y=\ \ \ 612}$ $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 67x\ \ \ \ \ \ \ \ \ \ \ =\ \ \ 268$ Solve for x. $67x=268$ $67x\div67=268\div67$ $x=4$ Substitute 4 for x in either equation and solve for y. $3(4)+8y=68$ $12+8y-12=68-12$ $8y=56$ $8y\div8=56\div8$ $y=7$
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