Answer
$b=\sqrt[5]{\frac{C}{A}} (A\ne0)$
Work Step by Step
First, divide both sides by $A$ to get $$b^5=\frac{C}{A}$$ Finally, take the fifth root to get $$b=\sqrt[5]{\frac{C}{A}}$$ (Note that $A$ cannot equal zero since it is being divided by in step one.)