[tex]\bf\\
3\sqrt{45} - \sqrt{125} + \sqrt{200} - \sqrt{50} =\\\\
=3\sqrt{9\times 5} - \sqrt{25 \times 5} + \sqrt{100\times 2} - \sqrt{25\times 2} =\\\\
=3\times 3\sqrt{5} - 5\sqrt{5} + 10\sqrt{2} - 5\sqrt{2} =\\\\
=9\sqrt{5} - 5\sqrt{5} + 10\sqrt{2} - 5\sqrt{2} = \boxed{\bf 4\sqrt{5} + 5\sqrt{2} }
[/tex]
