Tính

Tính : 
a) $\left(\frac{3^{6 }.{45}^4-{15}^{13}.5^{-9}}{{27}^4.{25}^3+{45}^6}\right)$​
b) $\frac{{\left(\frac{2}{5}\right)}^7.5^7+{\left(\frac{9}{4}\right)}^3 : {\left(\frac{3}{16}\right)}^3}{2^7.5^2+512}$