a, 0,5x - $\frac{2}{3}$x = $\frac{7}{12}$
(0,5 - $\frac{2}{3}$)x = $\frac{7}{12}$
$\frac{-1}{6}$ . x = $\frac{7}{12}$
x = $\frac{7}{12}$ : $\frac{-1}{6}$
x = $\frac{-7}{2}$
d, ($\frac{3x}{7}$ + 1) : (-4) = $\frac{-1}{28}$
$\frac{3x}{7}$ + 1 = $\frac{-1}{28}$ . (-4)
$\frac{3x}{7}$ + 1 = $\frac{1}{7}$
$\frac{3x}{7}$ = $\frac{1}{7}$ - 1
$\frac{3x}{7}$ = $\frac{-6}{7}$
=> 3x = -6
=> x = -2
