$a$) `0,5x - 2/3x = 5/6`
`⇔ x (1/2 - 2/3) = 5/6`
`⇔ x . -1/6 = 5/6`
`⇔ x = -5`
Vậy $x=-5$
$b$) `{3}/{x+60} = 60\%`
`⇔ 3/{x+60} = {60}/100`
`⇔ 3/{x+60} = 3/5`
`⇔ x + 60 = 5`
`⇔ x = -55`
Vậy `x=-55`
$c$) `1/5 .x + 4/5 . x = {(-3)^2}/{2}`
`⇔ x . (1/5 + 4/5) = 9/2`
`⇔ x . 1 = 9/2`
`⇔ x = 9/2`
Vậy `x=9/2`
$d$) `x/3 - x/4 = -1 5/12`
`⇔ {4x-3x}/12 = - 17/12`
`⇔ x = -17`
Vậy `x=-17`