`(5-\sqrt{15})/(\sqrt{5}-\sqrt{3})-2/(\sqrt{5}+\sqrt{3})`
`=(\sqrt{5}(\sqrt{5}-\sqrt{3}))/(\sqrt{5}-\sqrt{3})-(2(\sqrt{5}-\sqrt{3}))/((\sqrt{5}+\sqrt{3})(\sqrt{5}-\sqrt{3}))`
`=\sqrt{5}-(2(\sqrt{5}-\sqrt{3}))/(5-3)`
`=\sqrt{5}-(2(\sqrt{5}-\sqrt{3}))/2`
`=\sqrt{5}-(\sqrt{5}-\sqrt{3})`
`=\sqrt{5}-\sqrt{5}+\sqrt{3}`
`=\sqrt{3}`