Answer
$$9\cdot \:3^{\frac{2}{3}}n^{\frac{2}{3}}$$
Work Step by Step
Simplifying the expression using the rules of radicals, we find:
$$ \frac{3^2\cdot \:3^{\frac{2}{3}}\left(mn^2\right)^{\frac{2}{3}}}{\left(mn\right)^{\frac{2}{3}}}\\ \frac{3^2\cdot \:3^{\frac{2}{3}}m^{\frac{2}{3}}n^{\frac{4}{3}}}{m^{\frac{2}{3}}n^{\frac{2}{3}}}\\ 9\cdot \:3^{\frac{2}{3}}n^{\frac{2}{3}}$$
