`a)`

`4/3 + (1,25 - x) = 2,25`

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

`5/4 - x = 9/4 - 4/3`

`5/4 - x = 11/12`

`x = 5/4 - 11/12`

`x = 1/3`

Vậy `x = 1/3`

`b)`

`17/6 - (x - 7/6) = 7/4`

`x - 7/6 = 17/6 - 7/4`

`x - 7/6 = 13/12`

`x = 13/12 + 7/6`

`x = 9/4`

Vậy `x = 9/4`

`c)`

`-2/3 : x + 5/8 = -7/12`

`-2/3 : x = -7/12 - 5/8`

`-2/3 : x = -29/24`

`x = -2/3 : (-29/24)`

`x = 16/29`

Vậy `x = 16/29`

`d)`

`-2x - 5/6 = 7/12`

`-2x = 7/12 + 5/6`

`-2x = 17/12`

`x = 17/12 : (-2)`

`x = -17/24`

Vậy `x = -17/24`

`e)`

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

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

`x = 6/2 + 1/2`

`x = 7/2`

Vậy `x = 7/2`

`f)`

`1/3 x + 2/5 (x+1) = 0`

`1/3 x + 2/5 x + 2/5 = 0`

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

`x(5/15 + 6/15) = -2/5`

`11/15 x = -2/5`

`x = -2/5 : 11/15`

`x = -6/11`

Vậy `x = -6/11`