Ответ:

а) \(\frac{2}{5}+\frac{4}{10}=\frac{4}{10}+\frac{4}{10}=\frac{8}{10}=\frac{4}{5}\).

б) \(\frac{2}{3}+\frac{1}{6}=\frac{4}{6}+\frac{1}{6}=\frac{5}{6}\).

в) \(\frac{3}{8}+\frac{1}{4}=\frac{3}{8}+\frac{2}{8}=\frac{5}{8}\).

г) \(\frac{3}{8}-\frac{1}{4}=\frac{3}{8}-\frac{2}{8}=\frac{1}{8}\).

Ответ: а) \(\frac{4}{5}\); б) \(\frac{5}{6}\); в) \(\frac{5}{8}\); г) \(\frac{1}{8}\).