[tex]\displaystyle\\~~~~3.3\sqrt{40}-4.3\sqrt{320}-3\sqrt{5}=\\\\=3.3\sqrt{4\times10}-4.3\sqrt{64\times5}-3\sqrt{5}=\\\\=3.3\times2\sqrt{10}-4.3\times8\sqrt{5}-3\sqrt{5}=\\\\=6.6\sqrt{10}-34.4\sqrt{5}-3\sqrt{5}=\\\\=\boxed{\bf6.6\sqrt{10}-37.4\sqrt{5}}[/tex]
