`a)`
`3\sqrt{2} + 5\sqrt{8} - 2\sqrt{50}`
`= 3\sqrt{2} + 5\sqrt{4.2} - 2\sqrt{25.2}`
`= 3\sqrt{2} + 10\sqrt{2} - 10\sqrt{2}`
`= 3\sqrt{2}`
`b)`
`(\sqrt{14} - \sqrt{7})/(1 - \sqrt{2})`
`= (\sqrt{7}(\sqrt{2} - 1))/(1 - \sqrt{2})`
`= -(\sqrt{7}(\sqrt{2} - 1))/(\sqrt{2} - 1)`
`= -\sqrt{7}`