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: 22

Answer

1285 messages

Work Step by Step

The cost of the bill is: $C=10+0.1(m-1000)$, where $m$= number of messages, assuming the person has sent over 1000 messages that month. For Miriam, we have: $38.50=10+0.1(m-1000)$ We solve for $m$: $m=1000+(38.50-10)/0.1=1000+285=1285$ Thus she sent $1285$ messages in June.
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