First, subtract color(red)(2pir^2)2πr2 from each side of the equation to isolate the hh term:
S - color(red)(2pir^2) = 2pirh + 2pir^2 - color(red)(2pir^2)S−2πr2=2πrh+2πr2−2πr2
S - 2pir^2 = 2pirh + 0S−2πr2=2πrh+0
S - 2pir^2 = 2pirhS−2πr2=2πrh
Now, divide each side of the equation by color(red)(2pir)2πr to solve for hh:
(S - 2pir^2)/color(red)(2pir) = (2pirh)/color(red)(2pir)S−2πr22πr=2πrh2πr
(S - 2pir^2)/color(red)(2pir) = (color(red)(cancel(color(black)(2pir)))h)/cancel(color(red)(2pir))
(S - 2pir^2)/color(red)(2pir) = h
h = (S - 2pir^2)/color(red)(2pir)
Or
h = S/color(red)(2pir) - (2pir^2)/color(red)(2pir)
h = S/(2pir) - (color(red)(cancel(color(black)(2pi)))r^2)/cancel(color(red)(2pir))
h = S/(2pir) - r^2/r
h = S/(2pir) - r