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

`=> (3x-1) : 1/2 = 1/3 + 1`

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

`=>3x-1=4/3 . 1/2` 

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

`=>3x=5/3`

`=>x=5/9`

Vậy `x=5/9`

``

 b) `|1,3 - 1/4x| = 2,6`

TH1: `1,3 -1/4x=2,6`

`=>1/4x=-1,3`

`=>x=-26/5`

TH2: `1,3- 1/4 x=-2,6`

`=>1/4 x=-3,9`

`=>x=-78/5` (Không thỏa mãn)

Vậy `x=-26/5`

``

c) `(3x-1/2)^3+2.(-7)^2 :5^3=1`

`=>(3x-1/2)^3 + 98/125=1`

`=>(3x-1/2)^3 = 27/125`

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

`=>3x-1/2=3/5`

`=>3x=11/10`

`=>x=11/30`

Vậy `x=11/30`