A=2*3.14*r^2+2*3.14*rh

Supposed to be

A = 2\pi r^2 + 2\pi rh

Move the term with r^2

A - 2\pi r^2= 2\pi rh

Then divide by 2\pi r

\frac{A - 2\pi r^2}{2\pi r} = h

^ that was a typing error. I am not very used to them. Ok I've corrected it now. It's OK?