110

a)
\left(\frac{5}{4}\right)^{-2}+5^{-1}=\frac{16}{25}+\frac{1}{5}=\frac{21}{25}
b)
\left(\frac{1}{2x}\right)^{-3}-\left(-2x\right)^3=8x^3+8x^3=16x^3
c)
\left(7x\right)^{11}\cdot\left(\frac{7}{x}\right)^{-9}=\frac{7^{11}x^{11}}{1}\cdot\frac{x^9}{7^9}=\frac{7^2x^{20}}{1}=49x^{20}