a) `x - 2/5 = -9/10`
`⇒ x = -9/10 + 2/5`
`⇒ x = -1/2`
b) `3/4 + 1/4. x = -5/6`
`⇒ 1/4. x = -5/6 - 3/4`
`⇒ 1/4. x = -19/12`
`⇒ x = -19/12 : 1/4`
`⇒ x = -19/3`
c) `(x - 1)/3 = (2 - x)/-2`
`⇒ (x - 1). (-2) = 3. (2 - x)`
`⇒ -2x + 2 = 6 - 3x`
`⇒ -2x + 3x = 6 - 2`
`⇒ x = 4`
d) `|x + 1/2| - 1/3 = 0`
`⇒ |x + 1/2| = 1/3`
`TH1 : x + 1/2 = 1/3`
`⇒ x = 1/3 - 1/2`
`⇒ x = -1/6`
`TH2: x + 1/2 = -1/3`
`⇒ x = -1/3 - 1/2`
`⇒ x = -5/6`
Vậy `x = -1/6` hoặc `x = -5/6`
