Need help with basic GRE Math question

Greetings All,

I'm reviewing a GRE Math question from Princeton Review and I'm having trouble setting up an equation:

Question is: At the rate of *f*/3 feet per *m* minutes, how many feet can a bicycle travel in *s* seconds?

The answer is stated as *fs / *180*m*

But I don't know why or how the above equation is set up. I know that by using their plugging-in method, I can easily plug f=3, m=1, s=60 to have the answer at 1 ft per 1 minute, thus the above formula is the only correct formula, but I would like to understand how to set up an equation so that I can set up problems algebraically when I encounter them during the exam.

Many thanks in advance for all your help.