`a)`

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

`<=> (2.4 - 3x)/4 >= (3.2 + x-1)/4`

`<=> (8-3x)/4 >= (6+x-1)/4`

`<=> (8-3x)/4 >= (5+x)/4`

`<=> 8-3x-5-x >=0`

`<=>3-4x >= 0`

`<=> 4x <= 3`

`<=> x <= 3/4`

Vậy `S={x| x<= 3/4}`.

`b)`

`(x-2)/6 + (x-1)/3 > 5/4 -x`

`<=> (2.(x-2)+4.(x-1))/12 > (5.3-12.x)/12`

`<=>2x-4+4x-4 > 15-12x`

`<=>6x-8 > 15-12x`

`<=> 6x+12x > 15+8`

`<=> 18x > 23`

`<=> x > 23/18`

Vậy `S={x| x> 23/18}`.

`c)`

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

`<=> (3.(3x-2)-4.8)/24 <= (6.(2x-1)+12)/24`

`<=>9x-6-32 <= 12x-6+12`

`<=>9x-38 <= 12x+6`

`<=>9x-12x <= 6+38`

`<=>-3x <= 44`

`<=> x >= -44/3`

Vậy `S={x| x>= -44/3}`.