\(\frac{2^3+2^4+2^5}{7^2}=\frac{2^3.\left(1+2+2^2\right)}{7^2}=\frac{2^3.\left(1+2+4\right)}{7^2}=\frac{2^3.7}{7^2}=\frac{2^3}{7}=\frac{8}{7}\)
\(\frac{2^{15}.9^4}{6^6.8^3}=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^6.\left(2^3\right)^3}=\frac{2^{15}.3^8}{2^6.3^6.3^9}=\frac{2^{15}.3^8}{2^{15}.3^6}=3^2=9\)