Answer:
second one
s/(2πh) = r
Explanation:
You want to put the unknown value you are solving on 1 side and rest on the other side. In this case, you have to have r alone on one side.
s=2πrh
Since they are all multiplied with r, you divide them all on both sides to send them to other side.
s/(2πh) = 2πrh/ (2πh)
cancel out right side and it leaves r alone.
s/(2πh) = r