`a, |2x - 1/2| = 0,25`

`2x - 1/2 = 0,25` hoặc `2x-1/2  = -0,25`

`2x - 1/2 = 1/4` hoặc `2x-1/2= (-1)/4`

`2x=1/4 + 1/2` hoặc `2x= (-1)/4 + 1/2`

`2x= 3/4` hoặc `2x=1/4`

`x=3/8` hoặc `x=1/8`

Vậy `x in {3/8; 1/8}`

``

`b, 2/3 . x = sqrt{49}`

`2/3 . x = 7`

`x=7:2/3`

`x=7 . 3/2`

`x= 21/2`

``

`c, 2/3 - x = |0,25 - 1/2|`

`2/3 - x = |1/4-1/2|`

`2/3-x= |-1/4|`

`2/3-x = 1/4`

`x=2/3 - 1/4`

`x= 8/12 - 3/12`

`x=5/12`