## College Algebra (6th Edition)

$r= 1-\frac{C}{S}$
$S=\frac{C}{1-r}$ Solve for $r$ $S(1-r)= C$ $S-Sr=C$ $S-C=Sr$ $\frac{S-C}{S}=r$ or $r= 1-\frac{C}{S}$