$\textit{Đáp án + Giải thích các bước giải:}$
$\text{$\bigg(8 - \dfrac{9}{4} + \dfrac{2}{7}\bigg)$ - $\bigg(-6 - \dfrac{3}{7} + \dfrac{5}{4}\bigg)$ - $\bigg(3 + \dfrac{2}{4} - \dfrac{9}{7}\bigg)$}$
$\text{= 8 - $\dfrac{9}{4}$ + $\dfrac{2}{7}$ + 6 + $\dfrac{3}{7}$ - $\dfrac{5}{4}$ - 3 - $\dfrac{2}{4}$ + $\dfrac{9}{7}$}$
$\text{= (8 + 6 - 3) - $\bigg(\dfrac{9}{4} + \dfrac{5}{4} + \dfrac{2}{4}\bigg)$ + $\bigg(\dfrac{2}{7} + \dfrac{3}{7} + \dfrac{9}{7}\bigg)$}$
$\text{= 11 - 4 + 2}$
$\text{= 9}$
