Substitute $\displaystyle-{3}\usepackage{cmbright}\Huge\$ for x: $\displaystyle{{\left({4}{x}\right)}}^{{4}}={{\left({4}\cdot{\left(-{3}\right)}\right)}}^{{4}}\usepackage{cmbright}\Huge\$ . Remember that a negative number raised to the fourth power equals a positive number. The correct answer is 20,736.