If you would like to solve S = 2 * 3.14 * r^2 + 2 * 3.14 * r * h for h, you can do this using the following steps:
S = 2 * 3.14 * r^2 + 2 * 3.14 * r * h
S - 2 * 3.14 * r^2 = 2 * 3.14 * r * h /2
S/2 - 3.14 * r^2 = 3.14 * r * h /3.14
S/6.28 - r^2 = r * h /r
h = S/(6.28*r) - r
The correct result would be h = S/(6.28*r) - r.