\[\frac{9^{5} \cdot 81^{6}}{3^{30}} = \frac{\left( 3^{2} \right)^{5} \cdot \left( 3^{4} \right)^{6}}{3^{30}} =\]
\[= \frac{3^{10} \cdot 3^{24}}{3^{30}} = \frac{3^{34}}{3^{30}} = 3^{4} = 81\]