Đáp án`+`Giải thích các bước giải:

Bài `4:`

`a, 3/7 + (-5/6)`

`= 18/42 + (-35/42)`

`= (18 + (-35))/42`

`= -17/42.`

`b, 5,28 - 1,545`

`= 3,735.`

`c, -1 5/6 + 1,75`

`= -11/6 + 7/4`

`= -22/12 + 21/12`

`= -1/12.`

`d, -2,593 - 2/5`

`= -2,593 - 0,4`

`= -2,993.`

Bài `5:`

`6,5 - [0,75 - (8,25 - 1,75)]`

`= 6,5 - [0,75 - 6,5]`

`= 6,5 - (-5,75)`

`= 6,5 + 5,75`

`= 12,25.`

Bài `6:`

`a, -3x + 1/2 = 2 - 4/3`

`=> -3x + 1/2 = 6/3 - 4/3`

`=> -3x + 1/2 = 2/3`

`=> -3x = 2/3 - 1/2`

`=> -3x = 4/6 - 3/6`

`=> -3x = 1/6`

`=> x = 1/6 : -3`

`=> x = 1/6 . -1/3`

`=> x = -1/18`

Vậy `x = -1/18.`

`b, 0,75 - 5/6x = 2 - 2/3`

`=> 3/4 - 5/6x = 6/3 - 2/3`

`=> 3/4 - 5/6x = 4/3`

`=> 5/6x = 3/4 - 4/3`

`=> 5/6x = 9/12 - 16/12`

`=> 5/6x = -7/12`

`=> x = -7/12 : 5/6`

`=> x = -7/12 . 6/5`

`=> x = -7/10`

Vậy `x = -7/10.`

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