Correct. The power rule says $\displaystyle{{\left({{x}}^{{a}}\right)}}^{{b}}={{x}}^{{{a}\cdot{b}}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{\left({{x}}^{{3}}\right)}}^{{4}}={{x}}^{{{3}\cdot{4}}}={{x}}^{{12}}\usepackage{cmbright}\Huge\$ .