Đáp án:

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`8,`

`2 (3/2 - x) -1/2 = 7x - 1/4`

`↔ 3 - 2x - 1/2 = 7x - 1/4`

`↔ -2x + (3 - 1/2) = 7x - 1/4`

`↔ -2x + 5/2 = 7x - 1/4`

`↔ -2x - 7x = -5/2 - 1/4`

`↔ -9x = (-11)/4`

`↔ x = (-11)/4 ÷ (-9)`

`↔ x = 11/36`

Vậy `x =11/36`

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`9,`

`1/5 ( (-3)/5 - 10) + 5x = x - 2/3`

`↔ 1/5 × (-53)/5 + 5x = x - 2/3`

`↔ 5x -53/25 = x - 2/3`

`↔ 5x - x = 53/25 - 2/3`

`↔ 4x = 109/75`

`↔ x = 109/75 ÷ 4`

`↔ x = 109/300`

Vậy `x = 109/300`

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`10,`

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

`↔ (-3)/2 × 9/2 + 4 = (x - 1/2) - 1`

`↔ (-27)/4 + 4 = (x - 1/2) - 1`

`↔ (x-1/2) - 1 = (-11)/4`

`↔ x - 1/2 = (-11)/4 + 1`

`↔ x - 1/2 = (-7)/4`

`↔ x = (-7)/4 + 1/2`

`↔ x = (-5)/4`

Vậy `x=(-5)/4`

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`11,`

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

`↔ 1/3x - 2/3 = 1/2 × (-15)/4`

`↔ 1/3x - 2/3 = (-15)/8`

`↔ 1/3x = (-15)/8 + 2/3`

`↔ 1/3x = (-29)/24`

`↔ x = (-29)/24 ÷ 1/3`

`↔  x=(-29)/8`

Vậy `x=(-29)/9`

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`12,`

`2/5 - 1/3 (x - 1/2) = (x - 1/2) - 1`

`↔ 2/5 - 1/3x+ 1/6 = x - 1/2 - 1`

`↔ -1/3x + (2/5  + 1/6) = x + (-1/2-  1)`

`↔ -1/3x + 17/30 = x -3/2`

`↔ -1/3x - x = -17/30 - 3/2`

`↔ -4/3x = (-31)/15`

`↔ x = (-31)/15 ÷ (-4)/3`

`↔ x = 31/20`

Vậy `x=31/20`

`13,`

`-2 (x - 1/2) - 5 (3/10 - 1) = 7`

`↔ -2x + 1 - 3/2 + 5=  7`

`↔ -2x + (1 - 3/2 + 5) = 7`

`↔ -2x + ( (-1)/2 + 5) = 7`

`↔ -2x + 9/2 = 7`

`↔ -2x = 7 - 9/2`

`↔ -2x = 5/2`

`↔ x = 5/2 ÷ (-2)`

`↔ x = 5/2 × (-1/2)`

`↔ x = (-5)/4`

Vậy `x=(-5)/4`

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`14,`

`(-2)/3 (3/2 - x) - (3/4 - x) =3/4 (1/6 - 2/9)`

`↔ -1 + 2/3x - 3/4+ x = 3/4 × (-1)/18`

`↔ (-1 - 3/4) + (2/3x + x) = (-1)/24`

`↔ (-7)/4 + 5/3x = (-1)/24`

`↔ 5/3x = (-1)/24 - (-7)/4`

`↔ 5/3x = 41/24`

`↔ x = 41/24 ÷   5/3`

`↔ x = 41/24 × 3/5`

`↔ x = 41/40`

Vậy `x=41/40`

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`15,`

`3/4 (x - 8) = 5/7 (14 - 1/2)`

`↔ 3/4x - 6 = 5/7 × 27/2`

`↔ 3/4x - 6 = 135/14`

`↔ 3/4x = 135/14 + 6`

`↔ 3/4x = 219/14`

`↔ x = 219/14 ÷ 3/4`

`↔ x = 219/14 × 4/3`

`↔ x = 146/7`

Vậy `x=146/7`