Answer :
The given formula is
[tex]V=\frac{2}{15}\pi r^3[/tex]To solve for r, first, we need to multiply the equation by 15
[tex]\begin{gathered} 15V=15\cdot\frac{2}{15}\pi r^3 \\ 15V=2\pi r^3 \end{gathered}[/tex]Now, we divide the equation by 2pi
[tex]\begin{gathered} \frac{15V}{2\pi}=\frac{2\pi r^3}{2\pi} \\ \frac{15V}{2\pi}=r^3 \end{gathered}[/tex]Then, we take the cubic root on both sides
[tex]\begin{gathered} \sqrt[3]{\frac{15V}{2\pi}}=\sqrt[3]{r^3} \\ \sqrt[3]{\frac{15V}{2\pi}}=r \end{gathered}[/tex]Therefore, the formula solved for r is
[tex]r=\sqrt[3]{\frac{15V}{2\pi}}[/tex]