$-\dfrac{7}{8}:\dfrac{2}{7}-\Bigg(8-\dfrac{1}{3}x\Bigg)=\dfrac{5}{4}$
$⇔ -\dfrac{7}{8}.\dfrac{7}{2}-\dfrac{5}{4}=8-\dfrac{x}{3}$
$⇔ -\dfrac{69}{16}=8-\dfrac{x}{3}$
$⇔ \dfrac{x}{3}=8+\dfrac{69}{16}$
$⇔ \dfrac{x}{3}=\dfrac{197}{16}$
$⇔ x=3.\dfrac{197}{16}$
$⇔ x=\dfrac{591}{16}$