Đáp án:

d) -6

Giải thích các bước giải:

\(\begin{array}{l}
a)\left( {\dfrac{3}{4} - \dfrac{1}{4}} \right).\dfrac{6}{5}\\
 =  - \dfrac{1}{2}.\dfrac{6}{5} =  - \dfrac{3}{5}\\
c)\dfrac{{28}}{{15}}.\dfrac{1}{4}.3 + \left( {\dfrac{8}{{15}} - \dfrac{{79}}{{60}}} \right):\dfrac{{47}}{{24}}\\
 = \dfrac{7}{5}.\left( { - \dfrac{{47}}{{60}}} \right).\dfrac{{24}}{{47}}\\
 =  - \dfrac{{14}}{{25}}\\
b)\left( {\dfrac{3}{4} - \dfrac{1}{4}} \right):\dfrac{3}{7}\\
 = \dfrac{1}{2}.\dfrac{7}{3} = \dfrac{7}{6}\\
d)\left( {\dfrac{{10}}{3} + \dfrac{5}{2}} \right):\left( {\dfrac{{19}}{6} - \dfrac{{21}}{5}} \right) - \dfrac{{11}}{{31}}\\
 = \dfrac{{35}}{6}:\left( { - \dfrac{{31}}{{30}}} \right) - \dfrac{{11}}{{31}} =  - \dfrac{{175}}{{31}} - \dfrac{{11}}{{31}}\\
 =  - 6
\end{array}\)