You have simplified $\displaystyle{{\left({8}{x}\right)}}^{{4}}\usepackage{cmbright}\Huge\$ , but you have not used any of the properties of logarithms. The first step is to use the power property, $\displaystyle{\log}_{{{2}}}{{\left({8}{x}\right)}}^{{4}}={4}\cdot{\log}_{{{2}}}{8}{x}\usepackage{cmbright}\Huge\$ . You can rewrite further using the product property.