4(3x^2 y^4)^3/(2x^3y^5)^4
\(\frac{4(3x^2 y^4)^3}{(2x^3y^5)^4}\\~\\ \)
\(4*(3x^3y^4)^3\\ =4*(3*x^3*y^4)^3\\ =4*3^3*(x^3)^3*(y^4)^3\\ =4*27*x^{3*3}*y^{4*3}\\ =4*27*x^{9}*y^{12}\\\)
Now I have done what is necessary to simplify the top.
Now it is your turn to simplify the bottom.
After that you can put it back to one problem and cancel.