\(\frac{4^6.9^5+6^9.120}{8^4.3^{12}+6^{11}}\) \(=\) \(\frac{\left(2^2\right)^6.\left(3^2\right)^5+2^9.3^9.2^3.3.5}{\left(2^3\right)^4.3^{12}+2^{11}.3^{11}}\) \(=\) \(\frac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.3^{12}+2^{11}.3^{11}}\)
\(=\) \(\frac{2^{11}.3^{10}.\left(2+2.5\right)}{2^{11}.3^{10}.\left(2.3^2+3\right)}\) \(=\) \(\frac{2+10}{2.9+3}\) \(=\) \(\frac{12}{21}\) \(=\) \(\frac{4}{7}\)