Question 87991
 S = {{{(2(pi)rh + 2(pi)r^2)}}} 
 {{{(S - 2(pi)r^2)}}} = {{{(2(pi)rh + 2(pi)r^2 -2(pi)r^2)}}}
[isolate the h-term]
.

{{{(S - 2(pi)r^2)}}} = {{{(2(pi)rh)}}} 
 
{{{(S - 2(pi)r^2)/(2(pi)r))}}} = {{{(2(pi)rh)/(2(pi)r))}}}

.
{{{(S - 2(pi)r^2)/(2(pi)r))}}} = h
Check by substituting {{{(S - 2(pi)r^2)/(2(pi)r))}}} for the h-term in the original equation and simplify.