how to do this problem?

Question

you are choosing between two long-distnace telephone plans. Plan A has a monthly fee of $15 with a charge of $0.08 per minute for all long distance calls. Plan B has a monthly fee of $3 with a charge of $0.12 per minute for all long distnace calls. For how man minutes of long-distance calls will the costs for the two plans be the same>

Answer 1

 

12+0.08x = 3+0.12x; solve for x

Answer: x=300 minutes