I.
[tex]2\sqrt{18} + 3\sqrt{8} = 2\sqrt{9\cdot2} + 3\sqrt{4\cdot2} = 2\cdot\sqrt{9}\cdot\sqrt{2}+3\cdot\sqrt{4}\cdot\sqrt{2} = 2\cdot3\cdot\sqrt{2}+3\cdot2\cdot\sqrt{2} =\\\\=6\sqrt{2}+6\sqrt{2} =\boxed{12\sqrt{2}}[/tex]
II.
[tex]-4\sqrt{2}(3\sqrt{2}-1) = -4\sqrt{2}\cdot3\sqrt{2}-4\sqrt{2}\cdot(-1) = -12\sqrt{2\cdot2}+4\sqrt{2} = -12\cdot2 + 4\sqrt{2} =\\\\= \boxed{4\sqrt{2}-24}[/tex]
