Đề bài

Tính

a) $\dfrac{6}{7}.\left( { - \dfrac{1}{8}} \right) + \dfrac{6}{7}.\left( { - \dfrac{3}{4}} \right)$

b) $\left( {\dfrac{{ - 7}}{{17}}} \right).\dfrac{5}{{12}} + \left( {\dfrac{{ - 7}}{{17}}} \right).\dfrac{7}{{12}} + \left( {\dfrac{{ - 10}}{{17}}} \right)$

c) $\left[ {\dfrac{3}{5} + \left( {\dfrac{{ - 1}}{4}} \right)} \right]:\dfrac{3}{7} + \left[ {\left( {\dfrac{{ - 3}}{4}} \right) + \dfrac{2}{5}} \right]:\dfrac{3}{7}$

d) $\dfrac{7}{8}:\left( {\dfrac{2}{9} - \dfrac{1}{{18}}} \right) + \dfrac{7}{8}:\left( {\dfrac{1}{{36}} - \dfrac{5}{{12}}} \right)$