Вычислите: а) 7/9 + 5/12; б) 11/12 − 5/18; в) 3/8 + 19/20; г) 5/6 − 8/15.

1. \(\frac{7}{9}+\frac{5}{12}=\frac{28}{36}+\frac{15}{36}=\frac{43}{36}=1\frac{7}{36}\).
2. \(\frac{11}{12}-\frac{5}{18}=\frac{33}{36}-\frac{10}{36}=\frac{23}{36}\).
3. \(\frac{3}{8}+\frac{19}{20}=\frac{15}{40}+\frac{38}{40}=\frac{53}{40}=1\frac{13}{40}\).
4. \(\frac{5}{6}-\frac{8}{15}=\frac{25}{30}-\frac{16}{30}=\frac{9}{30}=\frac{3}{10}\).

Ответ: а) \(1\frac{7}{36}\); б) \(\frac{23}{36}\); в) \(1\frac{13}{40}\); г) \(\frac{3}{10}\).