Ответ:

а) \(\frac{1}{6}+\frac{1}{4}=\frac{2}{12}+\frac{3}{12}=\frac{5}{12}=\frac{10}{24}\).

\(\frac{23}{24}-\frac{10}{24}=\frac{13}{24}\).

б) \(\frac{3}{5}-\frac{4}{7}=\frac{21}{35}-\frac{20}{35}=\frac{1}{35}\).

\(\frac{4}{35}+\frac{1}{35}=\frac{5}{35}=\frac{1}{7}\).

в) \(\frac{2}{3}-\frac{3}{20}=\frac{40}{60}-\frac{9}{60}=\frac{31}{60}\).

\(\frac{11}{15}-\frac{31}{60}=\frac{44}{60}-\frac{31}{60}=\frac{13}{60}\).

Ответ: а) \(\frac{13}{24}\); б) \(\frac{1}{7}\); в) \(\frac{13}{60}\).