ABC Cable charges 120 dollars for installation plus 25 dollars a month. We do not know how many months we're working with, so we will have:
XYZ Cable charges 60 dollars for installation and 35 dollars per month. Again, we don't know how many months we're working with, but we know they will be the same, so we will have:
And, again, because we are finding the amount of months when the cost is the "same," we must set our rates equal.
120+25x = 60+35x
From here, we can solve for x, since is a single variable equation.
120 - 60 = 35x - 25x
60 = 10x
x = 6
Final answer is B, 6 months