\[\frac{a^{- 5}y^{6}}{a^{- 7}y^{7}} = \frac{a^{7}y^{6}}{a^{5}y^{7}} = a^{7 - 5} \cdot y^{6 - 7} =\]
\[= a^{2} \cdot y^{- 1} = \frac{a^{2}}{y}\]