a cellular phone company offers a contract for which the cost C in dollars of t minutes is given by C 0.25 (t-300)+ 61.95 where it is assumed that t¡Ý 300 minutes what time will keep $99.45 and 145.95
Solve 99.45 = 0.25 (t-300)+ 61.95
for time, t
Then repeat the process for
145.95 = 0.25 (t-300)+ 61.95