`\qquad (3\sqrt{2}+\sqrt{10})\sqrt{28-12\sqrt{5}}`
`=\sqrt{2}(3+\sqrt{5})\sqrt{28-12\sqrt{5}}`
`=(3+\sqrt{5})\sqrt{56-24\sqrt{5}}`
`=(3+\sqrt{5})\sqrt{36-2.6.(2\sqrt{5})+20}`
`=(3+\sqrt{5})\sqrt{(6-2\sqrt{5})^2}`
`=(3+\sqrt{5}).(6-2\sqrt{5})`
`=18-6\sqrt{5}+6\sqrt{5}-10`
`=8`