`a)`
`|x + 1/4| - 3/4 = 5%`
`⇒ |x + 1/4| - 15/20 = 1/20`
`⇒ |x + 1/4| = 16/20 = 4/5`
`⇒ x + 1/4 = 4/5 hoặc x + 1/4 = -4/5`
`⇒ x = 11/20 hoặc x = -21/20`
`Vậy S = {11/20 ; -21/20}`
`b)`
`2 - |3/2x - 1/4| = |(-5)/4|`
`⇒ 2 - |3/2x - 1/4|= 5/4`
`⇒ |3/2x - 1/4| = 2 - 5/4 = 3/4`
`⇒ 3/2x - 1/4 = 3/4 hoặc 3/2x - 1/4 = -3/4`
`⇒ x = 2/3 hoặc x = -1/3`
`Vậy S = {2/3 ; -1/3}`