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`