`a) \sqrt18 -2\sqrt50 +3\sqrt8`

`=\sqrt(9.2) -2\sqrt(25.2)+3\sqrt(4.2)`

`=3\sqrt2 -10\sqrt2 +6\sqrt2`

`=-\sqrt2`

`b) \sqrt((\sqrt7-4)^2) + \sqrt7`

`=|\sqrt7-4|+\sqrt7`

`=4-\sqrt7+\sqrt7`

`=4`

`c) \sqrt(3/20) + \sqrt(1/60) - 2\sqrt(1/15)`

`=\sqrt(15/100) + \sqrt(15/900) - 2\sqrt(15/(15^2))`

`=(\sqrt15)/10 + (\sqrt15)/30 - 2 (\sqrt15)/15`

`=(1/10 + 1/30 - 2/15) \sqrt15`

`=0.\sqrt15`

`=0`

`d) ((6-2\sqrt2)/(3-\sqrt2) + 5/(\sqrt5)) : 1/(2-\sqrt5)`

`=[(2(3-\sqrt2))/(3-\sqrt2) + \sqrt5] : 1/(2-\sqrt5)`

`=(2+\sqrt5) .(2-\sqrt5)`

`=4-5`

`=-1`

`e) (\sqrt10 -\sqrt2) \sqrt(3+\sqrt5)`

`=(\sqrt5 -1).\sqrt2 \sqrt(3+\sqrt5)`

`=(\sqrt5 -1). \sqrt(6+2\sqrt5)`

`=(\sqrt5-1)\sqrt(5+2\sqrt5+1)`

`=(\sqrt5-1).\sqrt((\sqrt5+1)^2)`

`=(\sqrt5-1)|\sqrt5+1|`

`=(\sqrt5-1)(\sqrt5+1)`

`=5-1`

`=4`