Question

S=a/1-r for solving for r

Answer 1

R = 1 - a/s is your answer

Hope this helped :)

Answer 2

$1 - r = \frac{a}{S}$

$r = 1 - \frac{a}{s}$

I think I have learned this before. Everytime you see many variables and 1, it'll always stay the same. So, all you have to do is multiply the variable (r) to remove it from the denominator. I know the my answer may not sound logic, but I hope this helps!