13) `(sqrt(28)-2sqrt(14)+sqrt(7))sqrt(7)+7sqrt(8)`
`=(sqrt(4.7)-2sqrt(2.7)+sqrt(7))sqrt(7)+7sqrt(4.2)`
`=(2sqrt(7)-2sqrt(7).sqrt(2)+sqrt(7))sqrt(7)+7.2sqrt(2)`
`=2.sqrt(7).sqrt(7)-2sqrt(7).sqrt(2).sqrt(7)+sqrt(7).sqrt(7)+14sqrt(2)`
`=2.7-2.7sqrt(2)+7+14sqrt(2)`
`=14-14sqrt(2)+7+14sqrt(2)`
`=21`
14) `(sqrt(14)-3sqrt(2))^2+6sqrt(28)`
`=(sqrt(14))^2-2.sqrt(14).3sqrt(2)+(3sqrt(2))^2+6sqrt(28)`
`=14-6sqrt(14.2)+9.2+6sqrt(28)`
`=14-6sqrt(28)+18+6sqrt(28)`
`=32`
15) `(sqrt(6)-sqrt(5))^2-sqrt(120)`
`=(sqrt(6))^2-2.sqrt(6).sqrt(5)+(sqrt(5))^2-sqrt(4.30)`
`=6-2.sqrt(30)+5-2sqrt(30)`
`=11-4sqrt(30)`
16) `(2sqrt(3)-3sqrt(2))^2+2sqrt(6)+3sqrt(24)`
`=(2sqrt(3))^2-2.2sqrt(3).3sqrt(2)+(3sqrt(2))^2+2sqrt(6)+3sqrt(4.6)`
`=4.3-12sqrt(6)+9.2+2sqrt(6)+3.2sqrt(6)`
`=12-12sqrt(6)+18+2sqrt(6)+6sqrt(6)`
`=30-12sqrt(6)+8sqrt(6)`
`=30-4sqrt(6)`
