a) $\frac{3}{7}+\frac{3}{7}/(-\frac{3}{2})-\frac{1}{2}=\frac{3}{7}+\frac{3}{7}\times (\frac{-2}{3})-\frac{1}{2}=\frac{3}{7}+(\frac{-2}{7})-\frac{1}{2}=\frac{1}{7}-\frac{1}{2}=\frac{-5}{14}$
b)$2\frac{1}{2}-(-\frac{1}{2})^{2}+\frac{3}{4}=\frac{5}{2}-\frac{1}{4}+\frac{3}{4}=\frac{5}{2}+\frac{1}{2}=3$
c) $(\frac{3}{8}-1.25)/(\frac{3}{4}-0.25)^{2}=(\frac{3}{8}-\frac{5}{4})/(\frac{3}{4}-\frac{1}{4})^{2}=(\frac{-7}{8})/(\frac{1}{2})^{2}=\frac{-7}{2}$
d) $1\frac{2}{5}/\frac{14}{15}+(1\frac{1}{3}-2\frac{1}{2})/\frac{5}{6}=\frac{7}{5}\times \frac{15}{14}+(\frac{4}{3}-\frac{5}{2})/\frac{5}{6}=\frac{3}{2}+(\frac{-7}{6}/\frac{5}{6}=\frac{1}{10}$