To find the area of a rectangle, you must multiply the length, $\displaystyle{6}{{a}}^{{6}}\usepackage{cmbright}\Huge\$ , times the width, $\displaystyle{2}{{a}}^{{2}}\usepackage{cmbright}\Huge\$ : $\displaystyle{6}{{a}}^{{6}}\cdot{2}{{a}}^{{2}}={6}\cdot{2}\cdot{{a}}^{{6}}\cdot{{a}}^{{2}}={12}{{a}}^{{{6}+{2}}}={12}{{a}}^{{8}}\usepackage{cmbright}\Huge\$