\(A.\frac{7}{8}-\frac{5}{12}=\frac{21}{24}-\frac{10}{24}=\frac{21-10}{24}=\frac{11}{24}\)
\(B.\frac{5}{6}-\frac{3}{10}=\frac{25}{30}-\frac{9}{30}=\frac{25-9}{30}=\frac{16}{30}=\frac{8}{15}\)
\(C.\frac{8}{15}-\frac{2}{5}=\frac{8}{15}-\frac{6}{15}=\frac{8-6}{15}=\frac{2}{15}\)
\(D.\frac{7}{10}-\frac{1}{5}=\frac{7}{10}-\frac{2}{10}=\frac{7-2}{10}=\frac{5}{10}=\frac{1}{2}\)