`a) \sqrt{27}-\sqrt{12}+2\sqrt{75}`
`=\sqrt{9.3}-\sqrt{4.3}+2\sqrt{25.3}`
`=3\sqrt{3}-2\sqrt{3}+2.5\sqrt{3}`
`=\sqrt{3}+10\sqrt{3}`
`=11\sqrt{3}`
`b) 3\sqrt{50}+\sqrt{200}-3\sqrt{72}`
`=3\sqrt{25.2}+\sqrt{100.2}-3\sqrt{36.2}`
`=3.5\sqrt{2}+10\sqrt{2}-3.6\sqrt{2}`
`=15\sqrt{2}+10\sqrt{2}-18\sqrt{2}`
`=7\sqrt{2}`