Correct. Use the Pythagorean Theorem:

$\displaystyle{{6}}^{{2}}+{{7}}^{{2}}={{z}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{36}+{49}={{z}}^{{2}}\usepackage{cmbright}\Huge\$

$\displaystyle{{z}}^{{2}}={85}\usepackage{cmbright}\Huge\$

$\displaystyle{x}\approx{9.2}\usepackage{cmbright}\Huge\$