You have the following information:
- Nicole purchased a pre paid card for $15
- Calls cost 16 cent, that is, $0.16 a minute
- Nicole made 1 call and hsa left $12.76 left on her card
In order to determine how many minutes she spent last call, you proceed as follow:
- First, subtract $12.76 to $15:
15 - 12.76 = 2.24
hence, she spent $2.24 in her last call.
- Next, divide the previoues result between the cost of each minute:
2.24/0.16 = 14
Hence, the call was of 14 minutes
An equation of the previous situation can be written as follow:
15 - 0.16x = 12.76
when the previoues equation is solved, you obtain exactly the same result:
x = 14 min