Question 1190846
Assume it is, (brackets help clarify things)

{{{S=((wd)/h)((h-d)/2)}}} make h the subject
multiply by 2h, get rid of the annoying fraction
2hS = wd(h-d)
2hS = wdh - wd^2
2hS - wdh = -wd^2
factor out h
h(2S - wd) = -wd^2
h = -{{{(wd^2)/((2S-wd))}}}