`a) ( 3/5 + \frac{-3}{4} + 1/20) : 1/2 - 1/2`
`= ( 12/20+ \frac{-15}{20} + 1/20) : 1/2 - 1/2`
`= -1/10 : 1/2 - 1/2`
`= -1/5 - 1/2`
`=-7/10`
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`b) 1 2/3 : 1/6 + 1 1/4 . ( 1/2 - 1/5)`
`= 5/3 : 1/6 + 5/4 . 3/10`
`= 10 + 3/8`
`= 83/8`
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`c)0,75 - ( 13/11 - 50%) : 5/11`
`= 3/4 - ( 13/11 - 1/2) . 11/5`
`= 3/4 - 15/22 . 11/5`
`= 3/4- 3/2`
`= 3/4 - 6/4`
`= -3/4`
---------------------------------------------------------
`d) 1/27 : (-1/3)^2 + 75% . ( -2 2/3)`
`= 1/27 : 1/9 + 3/4 . (-8/3)`
`= 1/3 + (-2)`
`= -5/3`
