2 years of local internet services cost $685, including the installation fee of $85. What is the monthly fee?

Question

What’s the monthly fee and what is the equation to find the answer 

Answer 1

2 years of local internet services cost $685, including the installation fee of $85. What is the monthly fee

685 - 85 = 600

(600/2yr)(1yr/12 mo) = x

x = 25/mo