Ta có :
$ \bigg(\dfrac{2}{3}-\dfrac{1}{2}\bigg).\dfrac{3}{4}-\dfrac{2}{5}.x =4 \dfrac{1}{4}$
$⇔ \dfrac{1}{6}.\dfrac{3}{4} - \dfrac{2}{5}.x = \dfrac{17}{4}$
$⇔ \dfrac{1}{8} - \dfrac{2}{5}.x = \dfrac{17}{4}$
$⇔\dfrac{2}{5}.x = \dfrac{-33}{8} $
$⇔x = \dfrac{-165}{16} $