Apply the power-of-a-power rule at each step:

$(x^4)^{5/4} = x^{4 \times 5/4} = x^5$

$(x^5)^{2/5} = x^{5 \times 2/5} = x^2$

Multiply using the product rule $x^a \cdot x^b = x^{a+b}$:

$x^5 \cdot x^2 = x^{5+2} = x^7$