Answer
$\dfrac{2m^4}{n^4}$
Work Step by Step
RECALL:
(i) $a^m \cdot a^n = a^{m+n}$
(ii) $a^{-m} = \dfrac{1}{a^m}, a\ne0$
(iii) $a^0=1, a\ne0$
Use the rules above to have:
$=\dfrac{10}{5}m^{6-2}n^{3-7}
\\=2m^4n^{-4}
\\=2m^4 \cdot \dfrac{1}{n^4}
\\=\dfrac{2m^4}{n^4}$
