\(\frac{4^{20}-2^{20}+6^{20}}{6^{20}-3^{20}+9^{20}}=\frac{\left(2^2\right)^{20}-2^{20}+\left(3.2\right)^{20}}{\left(3.2\right)^{20}-3^{20}+\left(3^2\right)^{20}}=\frac{2^{20}.2^{20}-2^{20}.1+3^{20}.2^{20}}{3^{20}.2^{20}-3^{20}.1+3^{20}.3^{20}}=\frac{2^{20}.\left(2^{20}-1+3^{20}\right)}{3^{20}.\left(2^{20}-1+3^{20}\right)}=\frac{2^{20}}{3^{20}}=\left(\frac{2}{3}\right)^{20}=\frac{40}{60}=\frac{2}{3}\)