`a)` `(-4,2).5,6 + 5,6.(-5,8) + 2,8`

`= 5,6.[(-4,2) + (-5,8)] + 2,8`

`= 5,6.(-10) + 2,8`

`= -56 + 2,8`

`= -53,2`

`-----`

b) `75% - 1 1/2 + 0,5 : 5/12`

`= 3/4 - 3/2 + 1/2 : 5/12`

`= 3/4 - 3/2 + 1/2 . 12/5`

`= 3/4 - 3/2 + 6/5`

`= 15/20 - 30/20 + 24/20`

`= 9/20`

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