System of Equations

Question

I call Cox Communications (a local cable company) to ask them about adding cable with DVR service. Their installation fee is waived since I'm a current customer (now you know I made this up) but has a monthly fee of $60. Then I call Direct TV whose monthly fee is only $40, but I have to pay a $100 installment fee. My question is, at what point (how many months) is my TOTAL cost the same for each option. Please show work.

Answer 1

I laughed at the "made-up" part. Ain't it the truth?!

 

So, let the number of months be "n"

 

0 + 60n = 100 + 40n

 

(60 - 40)n = 100 => n = 100 / 20

 

n = 5 months.