With an expression like this, you have to raise all the terms to the 3rd power. So the 5 will become [tex] 5^{3}=125 [/tex], [tex] x^{2} [/tex] will become [tex] (x^{2} )^3= x^{6} [/tex], the 4 will become [tex] 4^{3}=64 [/tex] and finally, the [tex]y^{4}[/tex] becomes [tex](y^{4})^3=y^{12}[/tex]. If you place all of these together in the same fraction, the new answer equivalent to the initial expression is [tex] \frac{125x^{6}}{64y^{12}} [/tex]