# How do you simplify (mn^(-4/5))^(-5/7)?

You can use the fact that ${\left({a}^{m}\right)}^{n} = {a}^{m \cdot n}$ and get:
${m}^{1 \cdot \left(- \frac{5}{7}\right)} {n}^{\left(- \frac{4}{5}\right) \cdot \left(- \frac{5}{7}\right)} = {m}^{- \frac{5}{7}} {n}^{\frac{4}{7}}$
If you want you can change them into roots using ${a}^{\frac{m}{n}} = \sqrt[n]{{a}^{m}}$ (and the fact that ${a}^{-} m = \frac{1}{a} ^ m$).