$\text{$5\sqrt{2}$ - $3\sqrt{18}$ + $2\sqrt{8}$.}$
$\text{= $5\sqrt{2}$ - $3\sqrt{3^2.2}$ + $2\sqrt{2^2.2}$.}$
$\text{= $5\sqrt{2}$ - $3.(3\sqrt{2})$ + $2.(2\sqrt{2}$).}$
$\text{= $5\sqrt{2}$ - $9\sqrt{2}$ + $4\sqrt{2}$.}$
$\text{= $-4\sqrt{2}$ + $4\sqrt{2}$.}$
$\text{= 0.}$