\(\dfrac{3^6.2^{10}}{2^8.3^8}=\dfrac{2^2}{3^2}=\dfrac{4}{9}\)
\(\dfrac{9^2.2^{10}}{16^2.81^2}=\dfrac{9^2.2^{10}}{\left(2^4\right)^2.\left(9^2\right)^2}=\dfrac{9^2.2^{10}}{2^8.9^4}\)
\(=\dfrac{9^2.2^8.2^2}{2^8.9^2.9^2}=\dfrac{2^2}{9^2}=\dfrac{4}{81}\)