We must reduce the fractions :

\(\dfrac{2^{10}.9^6}{4^6.3^{11}}=\dfrac{2^{10}.\left(3^2\right)^6}{\left(2^2\right)^6.3^{11}}=\dfrac{2^{10}.3^{12}}{2^{12}.3^{11}}=\dfrac{3}{2^2}\)

\(\dfrac{6^{12}}{9^5.2^{14}}=\dfrac{\left(2.3\right)^{12}}{\left(3^2\right)^5.2^{14}}=\dfrac{2^{12}.3^{12}}{3^{10}.2^{14}}=\dfrac{3^2}{2^2}\)

\(\dfrac{15^5.2^6.3^3}{5^6.6^8}=\dfrac{\left(3.5\right)^5.2^6.3^3}{5^6.\left(2.3\right)^8}=\dfrac{3^8.2^6.5^5}{3^8.2^8.5^6}=\dfrac{1}{2^2.5}\)

The smallest common denominator of 3 fractions is 2².5 = 20