\(A=\frac{2^{19}3^9+5.2^{18}3^9}{3^9.2^9.2^{10}+3^{10}4^{10}}=\frac{3^9\left(2^{19}+5.2^{18}\right)}{3^92^{19}+3^{10}2^{20}}=\frac{3^9\left(2^{19}+5.2^{18}\right)}{3^9\left(2^{19}+3.2^{20}\right)}=\frac{2^{19}+5.2^{18}}{2^{19}+3.2^{20}}=\frac{2^{18}\left(2+5\right)}{2^{18}\left(2+3.2^2\right)}\)
\(=\frac{2+5}{2+3.2^2}=\frac{7}{14}=\frac{1}{2}\)