a) $\frac{6}{7}.(−\frac{1}{8})+\frac{6}{7}.(\frac{−3}{4})=\frac{6}{7}.[(−\frac{1}{8}+(−\frac{3}{4})]=\frac{6}{7}.(−\frac{7}{8})=−\frac{3}{4}$

b) $(\frac{−7}{17}).\frac{5}{12}+(\frac{−7}{17}.\frac{7}{12}+(\frac{−10}{17})=(\frac{−7}{17}).(\frac{5}{12}+\frac{7}{12})+(\frac{−10}{17})=(\frac{−7}{17})+(\frac{−10}{17})$=−1

c)$[\frac{3}{5}+(\frac{−1}{4})]:\frac{3}{7}+[(\frac{−3}{4}+\frac{2}{5}]:\frac{3}{7}=[\frac{3}{5}+(\frac{−1}{4})+(\frac{−3}{4})+\frac{2}{5}].\frac{7}{3}$=0

d)$\frac{7}{8}:(\frac{2}{9}−\frac{1}{18})+\frac{7}{8}:(\frac{1}{36}−\frac{5}{12})=\frac{7}{8}:\frac{1}{6}+\frac{7}{8}:(\frac{−7}{18})$=3