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Bài 2:

`1)` `(x - 1/2) : 1/3 + 5/7 = 9 5/7`

`9 5/7 = 68/7`

`(x - 1/2) : 1/3 = 68/7 - 5/7 = 63/7 = 9`

`x - 1/2 = 9 xx 1/3 = 3`

`x = 3 + 1/2 = 7/2 = 3 1/2`

Vậy `x = 3 1/2.`

`2)` `11/13 - (5/42 - x) = -(15/28 - 11/13)`

`-(15/28 - 11/13) = 11/13 - 15/28 = 113/364`

`11/13 - 5/42 + x = 113/364`

`x = 113/364 - 11/13 + 5/42`

`= -5/12`

Vậy `x = -5/12.`

`3)` `(-1 1/5 + x) : (-3 3/5) = -7/4 + 1/4 : 1/8`

`1/4 : 1/8 = 2`

`-7/4 + 2 = 1/4`

`(-6/5 + x) : (-18/5) = 1/4`

`-6/5 + x = (-18/5) xx 1/4 = -9/10`

`x = -9/10 + 6/5 = 3/10`

Vậy `x = 3/10.`

`4)` `3/2 - (x - 2 1/3) = -3/4 - 1 1/8`

`2 1/3 = 7/3`

`-3/4 - 1 1/8 = -15/8`

`3/2 - x + 7/3 = -15/8`

`23/6 - x = -15/8`

`-x = -15/8 - 23/6 = -137/24`

`x = 137/24 = 5 17/24`

Vậy `x = 5 17/24.`

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

`3/4 : 22/9 = 27/88`

`27/88 - (-3x + 8/3) = 3/4`

`-3x + 8/3 = 27/88 - 3/4`

`-3x + 8/3 = -39/88`

`-3x = -39/88 - 8/3`

`-3x = -821/264`

`x = (-821/264) : (-3)`

`x = 821/792`

Vậy `x = 821/792`

`6)` `15/8 - 1/8 : (x/4 - 1/2) = 5/4`

`1/8 : (x/4 - 1/2) = 15/8 - 5/4 = 5/8`

`1/8 = 5/8(x/4 - 1/2)`

`1 = 5(x/4 - 1/2)`

`1/5 = x/4 - 1/2`

`x/4 = 1/5 + 1/2 = 7/10`

`x = 14/5`

Vậy `x = 14/5.`

`7)` `(-2/3x + 3/8) . (-8/5) = -8/15`

`-2/3x + 3/8 = 1/3`

`-2/3x = 1/3 - 3/8`

`-2/3x = -1/24`

`x = (-1/24) : (-2/3)`

`x = 1/16`

Vậy `x = 1/16`

`8)` `11/4 - [(x + 1/2)^3 - 15/12] = 5/8`

`15/12 = 5/4`

`11/4 - (x + 1/2)^3 + 5/4 = 5/8`

`4 - (x + 1/2)^3 = 5/8`

`(x + 1/2)^3 = 27/8`

`x + 1/2 = 3`

`x = 5/2`

Vậy `x = 5/2.`

Bài 3:

`1)` `2/3x − 1 2/5x = 3/5`

`2/3x − 7/5x = 3/5`

`(10/15 − 21/15)x = 3/5`

`−11/15x = 3/5`

`x = (3/5) : (−11/15)`

`x = 3/5 xx 15/11`

`x = −9/11`

Vậy `x = -9/11`

`2)` `2x − 3 = x + 1/2`

`2x − x = 3 + 1/2`

`x = 7/2`

`x = 7/2`

Vậy `x = 7/2`

`3)` `1/2x + 3/5x = −33/25`

`(5/10 + 6/10)x = −33/25`

`11/10x = −33/25`

`x = (−33/25) : (11/10)`

`x = −33/25 xx 10/11`

`x = −6/5`

Vậy `x = -6/5`

`4)` `5/2x − 1/3x + 2 = 3/2`

`5/2x − 1/3x = 3/2 − 2`

`15/6x − 2/6x = −1/2`

`13/6x = −1/2`

`x = (−1/2) : (13/6)`

`x = −1/2 xx 6/13`

`x = −3/13`

Vậy `x = −3/13`

`5)` `2/3x − 2/5 = 1/2x − 1/3`

`2/3x − 1/2x = 2/5 − 1/3`

`(4/6 − 3/6)x = (6/15 − 5/15)`

`1/6x = 1/15`

`x = 1/15 : 1/6`

`x = 6/15`

`x = 2/5`

Vậy `x = 2/5`

`6)` `1/2x + 2 1/2 = 3 1/2x − 3/4`

`1/2x + 5/2 = 7/2x − 3/4`

`5/2 + 3/4 = 7/2x − 1/2x`

`13/4 = 3x`

`x = 13/4 : 3`

`x = 13/12`

Vậy `x=13/12`

`7)` `1,5x − 2 1/3x = 1,5 − 2/3`

`3/2x − 7/3x = 3/2 − 2/3`

`(9/6 − 14/6)x = 5/6`

`−5/6x = 5/6`

`x = −1`

Vậy `x=-1`

`8)` `5/12x + 3 = 1/3 − 7/12x`

`5/12x + 7/12x = 1/3 − 3`

`12/12x = 1/3 − 9/3`

`x = −8/3`

Vậy `x = −8/3`

`9)` `1/6x + 1/10x − 4/15x + 1 = 0`

`(5/30 + 3/30 − 8/30)x + 1 = 0`

`0x + 1 = 0`

`1 = 0` (vô lí)

`=>` x không thỏa mãn đề bài