Correct. The values of a and b are not known, but they're equal, so the Pythagorean Theorem says that $\displaystyle{{c}}^{{2}}={{a}}^{{2}}+{{b}}^{{2}}={{a}}^{{2}}+{{a}}^{{2}}={2}{{a}}^{{2}}\usepackage{cmbright}\Huge\$ . Since $\displaystyle{c}={12}\usepackage{cmbright}\Huge\$ , $\displaystyle{2}{{a}}^{{2}}={{12}}^{{2}}={144}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{a}}^{{2}}={72}\usepackage{cmbright}\Huge\$ , and therefore $\displaystyle{a}=\sqrt{{{72}}}\usepackage{cmbright}\Huge\$ . Since $\displaystyle\sqrt{{{72}}}\usepackage{cmbright}\Huge\$ is approximately 8.4853, round the answer to 8.49 feet.