4.1)
`(7/10 +3/4 -20%) : (-0,5)^2`
`= (7/10 + 3/4 - 1/5) : (-1/2)^2`
`= (29/20 - 1/5) : (-1)^2/2^2`
`=5/4 : 1/4`
`= 5/4 .4`
`=5`
1) `3/8 -4/5 + 17/40`
`= -17/40 + 17/40`
`=0`
2) `-4/7 + 2/3 . (-9/14)`
`= -4/7 + (-3/7)`
`= -7/7`
`= -1`
3) `11/8 . 7/17 + 11/17.(-15/16) - 11/17`
`= 11/17 . 7/8 + 11/17.(-15/16) -11/17`
`= 11/17 (7/8 - 15/16 -1)`
`=11/17.(-17/16)`
`=-11/16`
5) `3 2/7 . 12 1/2 - 3 2/7 . 5 1/2`
`= 23/7 . 25/2 - 23/7 . 11/2`
`= 23/7(25/2 - 11/2)`
`= 23/7. 7`
`= 23`
