[tex]a] \ \sqrt{50}+3\sqrt2=\sqrt{25\cdot2}+3\sqrt2=5\sqrt2+3\sqrt2=8\sqrt2\\\\b] \ \frac{\sqrt{80}-\sqrt{20}}{\sqrt5}=\frac{\sqrt{16\cdot5}-\sqrt{4\cdot5}}{\sqrt5}=\frac{4\sqrt5-2\sqrt5}{\sqrt5}=\frac{2\sqrt5}{\sqrt5}=2\\\\c] \ \sqrt[3]{375}+\sqrt[3]{-81}=\sqrt[3]{125\cdot3}-\sqrt[3]{27\cdot3}=5\sqrt[3]3-3\sqrt[3]3=2\sqrt[3]3[/tex]