Simplify the following. Write numerical answers as fractions multiplied out and write expressions containing variables using positive exponents only.

(a) $\left(3^{2}\right)^{-2} =$

(b) $\displaystyle \left(\frac{5}{4}\right)^{-2} =$

(c) $\displaystyle \left(y^{7}\right)^{-5} =$