a) $\frac{6}{7}\times(-\frac{1}{8})+\frac{6}{7}\times(-\frac{3}{4})=\frac{6}{7}\times [(-\frac{1}{8}+(-\frac{3}{4})]=\frac{6}{7}\times (-\frac{7}{8})=-\frac{3}{4}$
b) $(\frac{-7}{17})\times\frac{5}{12}+(\frac{-7}{17}\times\frac{7}{12}+(\frac{-10}{17})=(\frac{-7}{17})\times (\frac{5}{12}+\frac{7}{12})+(\frac{-10}{17})=(\frac{-7}{17})+(\frac{-10}{17})=-1$
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}]\times \frac{7}{3}=0$
d) $\frac{7}{8}/(\frac{2}{9}-\frac{1}{18})+\frac{7}{8}/(\frac{1}{36}-\frac{5}{12})=\frac{7}{8}/\frac{1}{6}+\frac{7}{8}/(\frac{-7}{18})=3$