a) $3\frac{7}{8}-\frac{1}{4}=3\frac{7}{8}-\frac{2}{8}=3\frac{5}{8}$  

b) $6\frac{9}{16}-\frac{1}{2}=6\frac{9}{16}-\frac{8}{16}=6\frac{1}{16}$  

c) $3\frac{7}{10}-1\frac{2}{5}=3\frac{7}{10}-1\frac{4}{10}=2\frac{3}{10}$  

d) $6\frac{9}{14}-2\frac{3}{7}=6\frac{9}{14}-2\frac{6}{14}=4\frac{3}{14}$