3) $\frac{1}{2}$.x - $\frac{1}{4}$ = $\frac{-1}{2}$
$\frac{1}{2}$.x = $\frac{-1}{2}$ + $\frac{1}{4}$
$\frac{1}{2}$.x = $\frac{-1}{4}$
x = $\frac{-1}{4}$ : $\frac{1}{2}$
x = $\frac{-1}{4}$ . $\frac{2}{1}$
x = $\frac{-1}{2}$
Vậy x = $\frac{-1}{2}$
4) $\frac{1}{2}$ - $\frac{5}{6}$ : x = $\frac{2}{3}$
$\frac{5}{6}$ : x = $\frac{1}{2}$ - $\frac{2}{3}$
$\frac{5}{6}$ : x = $\frac{-1}{6}$
x = $\frac{5}{6}$ : $\frac{-1}{6}$
x = -5
Vậy x = -5
