a)
\sqrt{800}+\sqrt{80}-\sqrt{200}+\sqrt{500}=\sqrt{400*2}+\sqrt{16*5}-\sqrt{100*2}+\sqrt{100*5}=20\sqrt2+4\sqrt5-10\sqrt2+10\sqrt5=10\sqrt2+14\sqrt5
b)
\frac{\sqrt{12}-2\sqrt{27}}{\sqrt3}=\frac{(\sqrt{12}-2\sqrt{27})*\sqrt3}{\sqrt3*\sqrt3}=\frac{\sqrt{36}-2\sqrt{81}}{3}=\frac{6-2*9}{3}=
\frac{-12}{3}=-4
c)
\sqrt[4]{3}+\sqrt[4]{48}-\sqrt[4]{243}=\sqrt[4]{3}+\sqrt[4]{16*3} - \sqrt[4]{81*3} = \sqrt[4]{3} +2\sqrt[4]3 - 3\sqrt[4]3= 3\sqrt[4]3-3\sqrt[4]3=0