a) $\frac{8}{11}-1\frac{1}{4}+\frac{3}{14}-(\frac{-13}{21})+0.25=\frac{8}{21}+\frac{13}{21}-\frac{5}{4}+\frac{1}{4}+\frac{3}{14}=\frac{3}{14}$
b) $\frac{5}{8}\times 2\frac{2}{5}-\frac{5}{8}\times 1\frac{1}{3}=\frac{5}{8}\times (\frac{12}{5}-\frac{4}{3})=\frac{5}{8}\times \frac{16}{15}=\frac{2}{3}$
c) $(\frac{4}{9}-\frac{3}{5})/1\frac{1}{5}+(\frac{5}{9}+\frac{1}{5})/1\frac{1}{5}=(\frac{4}{9}-\frac{3}{5}+\frac{5}{9}+\frac{1}{5})/\frac{6}{5}=(1-\frac{2}{5})\times \frac{5}{6}=\frac{1}{2}$
d) $\frac{6}{7}/(\frac{3}{26}-\frac{3}{13})+\frac{6}{7}/(\frac{1}{10}-\frac{8}{5})=\frac{6}{7}/(\frac{3}{26}-\frac{6}{26})+\frac{6}{7}/(\frac{1}{10}-\frac{16}{10})=\frac{6}{7}\times [(\frac{-26}{3})+(\frac{-2}{3})]=-8$