Answer
$r=\sqrt[3]{\dfrac{3V}{4\pi}}$
Work Step by Step
Multiply $\frac{3}{4}$ to both sides to obtain:
$\frac{3}{4}V=\pi{r^3}$
Divide $\pi$ to both sides to obtain:
$\dfrac{\frac{3}{4}V}{\pi}=r^3
\\\dfrac{3V}{4\pi}=r^3$
Take the cube root of both sides to obtain:
$\sqrt[3]{\dfrac{3V}{4\pi}}=r$
