a) A = $\frac{3^{11}.11 + 3^{11}.21}{3^{9}2^{5}}$ = $\frac{3^{11}.(11+21)}{3^{9}2^{5}}$ = $\frac{3^{11}.2^{5}}{3^{9}2^{5}}$ = $3^{2}$ = 9
b) B = $\frac{2^{15}.7 - 2^{16}}{5.2^{15}}$ = $\frac{2^{15}.(7 - 2)}{5.2^{15}}$ = $\frac{2^{15}.5}{5.2^{15}}$ =1
c) C = $\frac{5. 7^{11} + 7^{12}}{7^{9}5^{2}-13.7^{9}}$ = $\frac{7^{11}(5+7)}{7^{9}(5^{2}-13)}$ = $\frac{7^{11}.12}{7^{9}.12}$ = $7^{2}$ = 49