Question

Martina purchased a prepaid phone card for $20. long distance calls cost 13 cents a minute using this card. Martina used her card only once to make a long distance call. If the remaining credit on her card is 17.92, how many minutes did her call last?

Answer 1

The call lasted 16 mins, i used trial and error and the came across 16x.13=2.08 and then you add 17.92 plus 2.08 and that gives you 20

Answer 2

Phone card = $20 
You need to minus 17.92 from 20 = $2.08 
$2.08 / 0.13 = how many minutes 
= 16