# How do you solve for r in S=2πrh?

$\frac{S}{2 \pi h} = r$
Divide both sides by $2 \pi h$ to get $r$ by itself on the right side:
$\frac{S}{2 \pi h} = \left(\cancel{\text{2"cancel"pi"rcancel"h")/(cancel"2"cancel"pi"cancel"h}}\right)$
$\frac{S}{2 \pi h} = r$