Question 971512
A:  $30 +$25 x, where x=number of months

B: $20 + $15 x

Set them equal

30 +25x = 20 +15 x
They will never be equal as the problem is stated.  The second one costs less to start and has fewer monthly charges.  Let me switch the monthly charges.

30 + 15x= 20 +25x
This will be equal at one month at $45.