[tex]27\sqrt{2}+7\sqrt{2}-9\sqrt{2} = 34\sqrt{2}-9\sqrt{2} = 25\sqrt{2}[/tex]
[tex]3(4\sqrt{3}-2\sqrt{5})+6(3\sqrt{5}+5\sqrt{3}) = 3\cdot4\sqrt{3}-3\cdot2\sqrt{5}+6\cdot3\sqrt{5}+6\cdot5\sqrt{3} =\\\\=12\sqrt{3}-6\sqrt{5}+18\sqrt{5}+30\sqrt{3} =42\sqrt{3}+12\sqrt5}[/tex]
