Answer:
$30.00 fee
$45.00=total bill
$0.10 per minute of usage
x = minutes used
$30.00 + 0.10 per minute = $45.00
$30.00+$0.10(x) = $45.00
$0.10(x) = $45.00-$30.00 = $15.00
x = $15.00/$0.10 = 150 minutes used
