## College Algebra 7th Edition

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.