a) `0,5.\sqrt{100}-1/4.\sqrt{16}+(-2/3)^{2}`
`= 0,5.10-1/4.`4`+(-2/3)^{2}`
`= 5-4/4+(-2/3)^{2}`
`= 5-1+4/9`
`= 4+4/9`
`= 40/9`
b) `5/17+2/3-20/12+7/9+12/17`
`= (5/17+12/17)+(2/3+7/9-20/12)`
`= 17/17+(24/36+28/36-60/36)`
`= 1+(52/36-60/36)`
`= 1+(-8/36)`
`= 36/36-8/36`
`= 28/36=7/9`