`5)` `frac{5\sqrt{2}-2\sqrt{5}}{\sqrt{10}}-frac{3}{\sqrt{5}-\sqrt{2}}`
`=frac{\sqrt{25.2}-\sqrt{5.4}}{\sqrt{10}}-frac{3(\sqrt{5}+\sqrt{2})}{(\sqrt{5}-\sqrt{2})(\sqrt{5}+\sqrt{2})}`
`=frac{\sqrt{50}-\sqrt{20}}{\sqrt{10}}-frac{3\sqrt{5}+3\sqrt{2}}{5-2}`
`=frac{\sqrt{10}(\sqrt{5}-\sqrt{2})}{\sqrt{10}}-frac{3(\sqrt{5}+\sqrt{2})}{3}`
`=\sqrt{5}-\sqrt{2}-(\sqrt{5}+\sqrt{2})`
`=\sqrt{5}-\sqrt{2}-\sqrt{5}-\sqrt{2}`
`=-2\sqrt{2}`