Many students like cross multiplication for problems like this. Write the fractions vertically, each with a top and a bottom. Draw a big X through the problem. This X will connect the 25 to the 12 and the 60 to the s.
The equation is then rewritten as
(25)(12) = (60)(s)
now divide both sides by 60 to get the variable you are solving for, s, alone:
(25)(12)/(60) = s
at this point, most students reach for their calculator. But I always ask students to look first if the problem can be reduced - many times it can be, and a calculator is not even necessary.
In this case the left side of the problem reduces to 25/5 = 5.
In fact, in the original problem, the 25/60 reduces by dividing a 5 out of both the top and bottom. This leads directly to an answer since 25/60 = (5x5)/(5x12) = 5/12. Comparing 5/12 to s/12 shows s=5.