[latex]\frac{z}{4}=\frac{8}{5}\\ 5z=32\\ x=\frac{32}{5} [/latex]

[latex]\frac{z}{4}=\frac{8}{5}\ \ \ \ \ |multiply\ both\ sides\ by\ 4\\\\z=4\times\frac{8}{5}\\\\z=\frac{32}{5}\\\\\boxed{z=6\frac{2}{5}=6.4}[/latex]