Answer:
14 minutes
Explanation:
In order to get the answer, we have to subtract the original amount of money on the phone card by the amount left over after the call:
15 - 12.76 = 2.24
Then, we divide this number by 0.16:
2.24 / 0.16 = 14
So, Heather's call lasted 14 minutes
Hope this helps :)