Substitute $\displaystyle-{3}\usepackage{cmbright}\Huge\$ for x: $\displaystyle{{\left({4}{x}\right)}}^{{4}}={{\left({4}\cdot{\left(-{3}\right)}\right)}}^{{4}}={{\left(-{12}\right)}}^{{4}}={20},{736}\usepackage{cmbright}\Huge\$