`a) \sqrt{0,2}.\sqrt{500}`
`=\sqrt{0,2.500}`
`=\sqrt{100}`
`=10`
`b) \sqrt{20}+\sqrt{80}-\sqrt{45}`
`=\sqrt{4.5}+\sqrt{16.5}-\sqrt{9.5}`
`=2\sqrt{5}+4\sqrt{5}-3\sqrt{5}`
`=3\sqrt{5}`
`c) 2/\sqrt{3}+\sqrt{1/3}+2\sqrt{27}-\sqrt{(sqrt{3}-2)^2}`
`=(2\sqrt{3})/3+\sqrt{3}/3+2.3\sqrt{3}-|\sqrt{3}-2|`
`=2/3\sqrt{3}+1/3\sqrt{3}+6\sqrt{3}-2+\sqrt{3}`
`=8\sqrt{3}-2`
`d) (\sqrt{10}-\sqrt{5})/(\sqrt{2}-1)-(3\sqrt{5}+5)/(\sqrt{5}+3)+2/\sqrt{2}`
`=(\sqrt{5}(\sqrt{2}-1))/(\sqrt{2}-1)-(\sqrt{5}(3+\sqrt{5}))/(\sqrt{5}+3)+\sqrt{2}`
`=\sqrt{5}-\sqrt{5}+\sqrt{2}`
`=\sqrt{2}`
