`x+1/2 =2`
`-> x = 2 -1/2`
`-> x = 4/2 -1/2`
`-> x = 3/2`
Vậy `x =3/2`
$\\$
`75%x - 1/2 = 1 1/4`
`-> 3/4x - 1/2 = 5/4`
`-> 3/4x = 5/4 +1/2 = 5/4 +2/4 = 7/4`
`-> x = 7/4 : 3/4 = 7/4 . 4/3 =7/3`
Vậy `x = 7/3`
$\\$
`|x-2/5| + 7/10 =3`
`-> |x-2/5| = 3 - 7/10 = 23/10`
`-> x -2/5 = 23/10` hoặc `x -2/5 = -23/10`
`->x = 27/10` hoặc `x = -19/10`
Vậy `x \in {27/10 ; -19/10}`