Correct. Use the variable c to represent the missing length. The Pythagorean Theorem says that $\displaystyle{{6}}^{{2}}+{{8}}^{{2}}={{c}}^{{2}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{{c}}^{{2}}={36}+{64}={100}\usepackage{cmbright}\Huge\$ , and therefore $\displaystyle{c}=\sqrt{{{100}}}={10}\usepackage{cmbright}\Huge\$ .