Incorrect. Hector applied the Distributive Property correctly when he multiplied $\displaystyle{3}{a}\cdot{b}\usepackage{cmbright}\Huge\$ to get 3ab. Now he also has to multiply $\displaystyle{3}{a}\cdot-{15}\usepackage{cmbright}\Huge\$ and $\displaystyle{3}{a}\cdot{7}{c}\usepackage{cmbright}\Huge\$ . What terms are missing?