Correct. To simplify an expression, reorder the addends and combine like terms. $\displaystyle{3}{{c}}^{{3}}{{d}}^{{2}}\usepackage{cmbright}\Huge\$ , $\displaystyle-{3}{{c}}^{{3}}{{d}}^{{2}}\usepackage{cmbright}\Huge\$ , and $\displaystyle{4}{{c}}^{{3}}{{d}}^{{2}}\usepackage{cmbright}\Huge\$ are like terms, and can be combined as follows: $\displaystyle{3}{{c}}^{{3}}{{d}}^{{2}}-{3}{{c}}^{{3}}{{d}}^{{2}}+{4}{{c}}^{{3}}{{d}}^{{2}}={\left({3}-{3}+{4}\right)}{{c}}^{{3}}{{d}}^{{2}}={4}{{c}}^{{3}}{{d}}^{{2}}\usepackage{cmbright}\Huge\$ . The coefficient is 4.