Answer
$r=1-\frac{C}{S}$
Work Step by Step
$S = \frac{C}{1-r}$
$S(1-r)=C$
$1-r=\frac{C}{S}$
$r=1-\frac{C}{S}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.