Factor $72=6^{2}\times 2$. Rewrite the square root of the product $\sqrt{6^{2}\times 2}$ as the product of square roots $\sqrt{6^{2}}\sqrt{2}$. Take the square root of $6^{2}$.
$$6\sqrt{2}+\sqrt{32}+\sqrt{18}$$
Factor $32=4^{2}\times 2$. Rewrite the square root of the product $\sqrt{4^{2}\times 2}$ as the product of square roots $\sqrt{4^{2}}\sqrt{2}$. Take the square root of $4^{2}$.
$$6\sqrt{2}+4\sqrt{2}+\sqrt{18}$$
Combine $6\sqrt{2}$ and $4\sqrt{2}$ to get $10\sqrt{2}$.
$$10\sqrt{2}+\sqrt{18}$$
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 $3^{2}$.
$$10\sqrt{2}+3\sqrt{2}$$
Combine $10\sqrt{2}$ and $3\sqrt{2}$ to get $13\sqrt{2}$.
