The answer is about 432.178
A has fixed one time fee of $12 and if you go to it say "m" months you pay $28 for each month, so your total cost at A is really 12 + 28m.
B has a fixed one time fee of $20 and if you go to it "m" months you pay $26 for each month, so you total cost at B is 20 + 26m.
how many months for the cost to be the same?

well, since the cost for both is the same, we can just get A's, knowing that B is the same

So, this is asking for any number that subtracts to = 16-7
Well, 16-7= 9 so use any two numbers that would subtract to equal 9
Like so:
11-2=9
18-9=9
34-25=9
-2-11=9
Etc....
Hope this helps! :)