A promotional deal for long distance phone service charges a $15 basic fee plus $0.05 per minute for

A promotional deal for long distance phone service charges a $15 basic fee plus $0.05 per minute for all calls. If Joe's phone bill was $60 under this promotional deal, how many minutes of phone calls did he make? Round to the nearest integer if necessary.

Let m be the number of minutes Joe used. We have a cost function of:
C(m) = 0.05m + 15

If C(m) = 60, then we have:
0.05m + 15 = 60

Typing this equation into our search engine, we get:
m = 900