Customers of a phone company can choose between two service plans for long distance calls. the first plan has an $18 monthly fee and charges an additional $0.07 for each minute of calls. the second plan has no monthly fee but charges $0.12 for each minute of calls. for how many minutes of calls will the costs of the two plans be equal?

We call x the minutes to talk
+ The first plan has an $18 monthly fee and charges an additional $0.07 for each minute of calls: The money for x minute is 28+0.07x
+ The second plan has no monthly fee but charges $0.12 for each minute of calls.And the  money is 0+ 0.12x
We have to solve the equation: 28+0.07x= 0+ 0.12x
or 0.12x-0.07x=28
0.05x=28 and we have x=28:0.05= 560.
For 560 minutes of calls will the costs of the two plans be equal