You may have simplified the radicals incorrectly by obtaining $\displaystyle{8}\cdot{6}\sqrt{{{2}}}-{4}\cdot{5}\sqrt{{{2}}}\usepackage{cmbright}\Huge\$ and simplifying to $\displaystyle{14}\sqrt{{{2}}}-{9}\sqrt{{{2}}}\usepackage{cmbright}\Huge\$ . When you pull a number out of the radical, it is multiplied by any coefficient already there, not added to it.