\(A=\frac{8^{10}+4^{10}}{8^4+4^{11}}\\ =\frac{8^4.8^6+4^{10}}{8^4+4^{10}.4}\\ =\frac{8^6}{4}\\ =\frac{262144}{4}\\ =65536\)
\(A=\frac{8^{10}+4^{10}}{8^4+4^{11}}=\frac{\left(2^3\right)^{10}+\left(2^2\right)^{10}}{\left(2^3\right)^4+\left(2^2\right)^{11}}=\frac{2^{30}+2^{20}}{2^{12}+2^{22}}=\frac{2^{20}\left(2^{10}+1\right)}{2^{12}\left(2^{10}+1\right)}=2^8=256\)
\(B=\frac{8^{11}.3^{17}}{27^{10}.9^{15}}=\frac{\left(2^3\right)^{11}.3^{17}}{\left(3^3\right)^{10}.\left(3^2\right)^{15}}=\frac{2^{33}.3^{17}}{3^{30}.3^{30}}=\frac{2^{33}}{3^{43}}\)
\(C=\frac{8^2.4^5}{2^{20}}=\frac{\left(2^3\right)^2.\left(2^2\right)^5}{2^{20}}=\frac{2^6.2^{10}}{2^{20}}=\frac{1}{2^4}=\frac{1}{16}\)