\[\left( \frac{a^{12}b^{- 4}\ }{c^{5}d^{- 13}} \right)^{- 2} = \frac{a^{- 24}b^{8}}{c^{- 10}d^{26}} =\]
\[= a^{- 24}b^{8}c^{10}d^{- 26}\]