`a)` `11/12 + 1/12 (2x - 1/4) = 13/16`

`11/12 + (2x)/12 - 1/48 = 13/16`

`11/12 + x/6 - 1/48 = 13/16`

`44/48 + (8x)/48 - 1/48 = 39/48`

`(8x)/48 = -4/48`

`8x = -4`

`x = -1/2`

`b)` `|1 - x| - 9/25 = (-4/5)^2`

`|1 - x| - 9/25 = 16/25`

`|1 - x| = 25/25 = 1`

`1 - x = 1` hoặc `1 - x = -1`

`x=0` hoặc `x=2`

`c)` Đặt `x = 5k, y = 4k, z = 6k`

Ta có :

`5k - 2(4k) + 6k = -6`

`5k - 8k + 6k = -6`

`3k=-6`

`k=-2`

`=>x=5(-2) = -10`

`y = 4(-2) = -8`

`z = 6(-2) = -12`