\(\frac{45^3.20^4.18^2}{180^5}=\frac{\left(3^2.5\right)^3.\left(2^2x5\right)^4.\left(2x3^2\right)^2}{\left(2^2.3^2.5\right)^5}\)
\(=\frac{3^6.5^3.2^8.5^4.2^2.3^4}{2^{10}.3^{10}.5^5}\)\(=\frac{3^{10}.5^7.2^{10}}{2^{10}.3^{10}.5^5}=\frac{5^7}{5^5}=5^2\)