Incorrect. Multiply length and height first, since they are the simplest terms. Multiplying $\displaystyle{12}\cdot{4}{x}\usepackage{cmbright}\Huge\$ gives you $\displaystyle{48}{x}\usepackage{cmbright}\Huge\$ , which is the area of one face on the cube. To find volume, multiply $\displaystyle{48}{x}\usepackage{cmbright}\Huge\$ by the width, which is $\displaystyle{3}{x}+{5}\usepackage{cmbright}\Huge\$ .