Answer
9 hours
Work Step by Step
Mark can do 1/20 = .05 jobs per hour while Phil can do 1/30 = .0333 jobs per hour. Let t be the time they worked together:
$1 = .05t + .033t + 5(.05) \\ .75 = .083t \\ t =9$
Elementary Algebra
by Kaufmann, Jerome; Schwitters, Karen;
Published by
Cengage Learning
ISBN 10:
1285194055
ISBN 13:
978-1-28519-405-9
Chapter 7 - Algebraic Fractions - 7.6 - More Fractional Equations and Problem Solving - Problem Set 7.6 - Page 315: 45
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