Factor $18=3^{2}\times 2$. Rewrite the square root of the product $\sqrt{3^{2}\times 2}$ as the product of square roots $\sqrt{3^{2}}\sqrt{2}$. Take the square root of $3^{2}$.
$$3\times 3\sqrt{2}-11\sqrt{2}+2\times 50$$
Multiply $3$ and $3$ to get $9$.
$$9\sqrt{2}-11\sqrt{2}+2\times 50$$
Combine $9\sqrt{2}$ and $-11\sqrt{2}$ to get $-2\sqrt{2}$.
