Đáp án:

Giải thích các bước giải:

bài 1 

a) ` 9/4 - 3/4 +1/3`

`= 6/4 +1/3`

`= 3/2 +1/3 `

`= 9/6 + 2/6`

`= 11/6`

b ) `34/15  -25/6 - 4/15 + 7/6`

`= 34/15 -4/15 - 25/6 + 7/6 `

`= 38/15 - 18/6 `

`= 38/15 - 45/15`

`=83/15`

c) 7/13 * 1 14/31 -37/31 : 13/7 + 7/13`

`= 7/13 * 45/31 -37/31 *7/13 + 7/13`

`=7/13 ( 45/31 -37/31 +1)`

`=7/13* 39/31`

`=21/31`

bài 2

a)` x - 2/3 = 35/21`

`<=>x = 35/21 + 2/3`

`<=>x= 49/21`

 `<=>x= 7/3 `

Vậy `x=7/3`

b)` 54/19 . x + 16/5 = 1/2 `

`<=>54/19 . x = 1/2 -16/5`

`<=>54/19 . x = -27/10`

 `<=>x = -27/10 : 54/19`

`<=>x = -19/20`

Vậy  `x=-19/20`

c) ` x-1/16 = -7/4`

`<=>x-1/16= -28/16`

`<=>x-1 = -28`

`<=>x = -28 - (-1)`

`<=>x = -28 + 1 `

`<=>x = -27 `

 Vậy `x=-27`