Rearrange the terms so that like radicals are next to each other. Then add those like terms.

$\displaystyle{7}\sqrt{{6}}+\sqrt{{7}}+{7}\sqrt{{6}}+\sqrt{{7}}={7}\sqrt{{{6}}}+{7}\sqrt{{{6}}}+\sqrt{{{7}}}+\sqrt{{{7}}}\usepackage{cmbright}\Huge\$

$\displaystyle={\left({7}+{7}\right)}\sqrt{{6}}+{\left({1}+{1}\right)}\sqrt{{7}}={14}\sqrt{{{6}}}+{2}\sqrt{{{7}}}\usepackage{cmbright}\Huge\$