$$\sqrt[3]{\frac{a^{l}}{a^{m}}}\times\sqrt[3]{\frac{a^{n}}{a^{n}}}\times\sqrt[3]{\frac{a^{n}}{a^{l}}}$$
$a^{\frac{n-m}{3}}$
$\frac{\left(n-m\right)a^{\frac{-m+n-3}{3}}}{3}$
