[tex]3\sqrt5-2\sqrt7+\sqrt{45}-\sqrt{28}\\\\=3\sqrt5-2\sqrt7+\sqrt{9\cdot5}-\sqrt{4\cdot7}\\\\=3\sqrt5-2\sqrt7+\sqrt9\cdot\sqrt5-\sqrt4\cdot\sqrt7\\\\=3\sqrt5-2\sqrt7+3\sqrt5-2\sqrt7\\\\=(3\sqrt5+3\sqrt5)+(-2\sqrt7-2\sqrt7)\\\\=\boxed{6\sqrt5-4\sqrt7}[/tex]