Đáp án `+` Giải thích các bước giải:

`a) 3/7 + (-9/5) - 4/3`

`= 45/105 - 189/105 - 140/105`

`= (45 - 189 - 140)/105`

`=-284/105`

`b) 5/4 - (-3 1/2) - 7/10`

`= 5/4 + 7/2 - 7/10`

`=50/40 + 140/40 - 28/40`

`= 81/20`

`c) 5/3 + (-2/7) - (-1,2)`

`= 5/3 - 2/7 + 6/5 `

`= 175/105 - 30/105 + 126/105`

`= (175 - 30 + 126)/105`

`= 271/105`

`d) -5/12 + 1 5/18 - 2,25 `

`= -5/12 + 23/18 - 9/4`

`= -15/36 + 46/36 - 81/36 `

`= ( -15 + 46 - 81 )/36 `

` = -25/18`

`e) 2 3/11 . 1 1/12 . (-2,2)`

`= 25/11 . 13/12 . (-11/5) `

`= 25/11 . (-11/5) . 13/12`

`= -5 . 13/12`

`= -65/12`

`g) 18/39 . (-1 5/8) : (-6 3/4)`

`= 6/13 . (-13/8) : (-27/4)`

`= -3/4 . (-4/27)`

`= -1/9`

`h) 3/5 + 2/5 . (-3/4)`

`= 3/5 - 3/10`

`= 6/10 - 3/10 `

`= 3/10`

`i) 2/3 - 5/3 : 3/4 + 25%`

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

`= 2/3 - 20/9 + 1/4`

`= 24/36 - 80/36 + 9/36`

`= (24 - 80 + 9)/36`

`= -47/36`

`k) 3/5 + 2/5 : (2 1/4 - 0,25)`

`= 3/5 + 2/5 : (9/4 - 1/4) `

`= 3/5 + 2/5 : 2`

`= 3/5 + 2/5 . 1/2`

`= 3/5 + 1/5 `

`= 4/5`