Đáp án:
$\begin{array}{l}
a)8\dfrac{3}{4} - \left( {2\dfrac{7}{9} + 4\dfrac{3}{4}} \right)\\
= 8\dfrac{3}{4} - 2\dfrac{7}{9} - 4\dfrac{3}{4}\\
= 4\dfrac{3}{4} - 2\dfrac{7}{9}\\
= \dfrac{{19}}{4} - \dfrac{{25}}{9}\\
= \dfrac{{171}}{{36}} - \dfrac{{100}}{{36}}\\
= \dfrac{{71}}{{36}}\\
b)\left( {1,5 + \dfrac{2}{3}} \right):\dfrac{3}{4} + \dfrac{1}{4}\\
= \left( {\dfrac{3}{2} + \dfrac{2}{3}} \right).\dfrac{4}{3} + \dfrac{1}{4}\\
= \dfrac{{13}}{6}.\dfrac{4}{3} + \dfrac{1}{4}\\
= \dfrac{{26}}{9} + \dfrac{1}{4}\\
= \dfrac{{113}}{{36}}\\
c)1\dfrac{2}{3} + \dfrac{5}{8} + \dfrac{{ - 5}}{3} + \dfrac{3}{8} - \dfrac{1}{2}\\
= \dfrac{5}{3} + \dfrac{{ - 5}}{3} + \left( {\dfrac{5}{8} + \dfrac{3}{8}} \right) - \dfrac{1}{2}\\
= 0 + 1 - \dfrac{1}{2}\\
= \dfrac{1}{2}
\end{array}$
