College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter P, Prerequisites - Section P.9 - Modeling with Equations - P.9 Exercises: 32

Answer

The assistant worked 35 hours and the plumber worked 70 hours.

Work Step by Step

Let's say that the assistant worked $t$ hours. Then the plumber worked $2*t$ hours. The final bill was \$4025: $4025=25*t+45*2t$ We solve for $t$: $4025=115*t$ $t=4025/115=35$ Thus the assistant worked 35 hours and the plumber worked 35*2=70 hours.
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