д) \(\frac{5}{12}+\frac{1}{6}\); е) \(\frac{3}{5}-\frac{4}{15}\); ж) \(\frac{19}{21}-\frac{11}{15}\); з) \(\frac{5}{42}+\frac{10}{63}\).

1. \(\frac{5}{12}+\frac{1}{6}=\frac{5}{12}+\frac{2}{12}=\frac{7}{12}\).

2. \(\frac{3}{5}-\frac{4}{15}=\frac{9}{15}-\frac{4}{15}=\frac{5}{15}=\frac{1}{3}\).

3. \(\frac{19}{21}-\frac{11}{15}=\frac{95}{105}-\frac{77}{105}=\frac{18}{105}=\frac{6}{35}\).

4. \(\frac{5}{42}+\frac{10}{63}=\frac{15}{126}+\frac{20}{126}=\frac{35}{126}=\frac{5}{18}\).

Ответ: д) \(\frac{7}{12}\); е) \(\frac{1}{3}\); ж) \(\frac{6}{35}\); з) \(\frac{5}{18}\).