Correct. Given $\displaystyle{c}={15}\usepackage{cmbright}\Huge\$ and $\displaystyle{a}={9}\usepackage{cmbright}\Huge\$ , the Pythagorean Theorem gives us $\displaystyle{{c}}^{{2}}={{a}}^{{2}}+{{b}}^{{2}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{15}}^{{2}}={{9}}^{{2}}+{{b}}^{{2}}\usepackage{cmbright}\Huge\$ , and therefore $\displaystyle{{b}}^{{2}}={{15}}^{{2}}-{{9}}^{{2}}={225}-{81}={144}\usepackage{cmbright}\Huge\$ , so $\displaystyle{b}=\sqrt{{{144}}}={12}\usepackage{cmbright}\Huge\$ .