и) \(\frac{7}{9}+\frac{5}{12}\); к) \(\frac{11}{12}-\frac{5}{18}\); л) \(\frac{3}{8}+\frac{19}{20}\); м) \(\frac{5}{6}-\frac{8}{15}\).

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: и) \(1\frac{7}{36}\); к) \(\frac{23}{36}\); л) \(1\frac{13}{40}\); м) \(\frac{3}{10}\).