4. Выполните действия: 1) 1/5 + 1/2; 2) 1/6 + 1/3; 3) 5/12 + 1/4; 4) 11/15 − 3/10 + 1/45.

1. \(\frac{1}{5}+\frac{1}{2}=\frac{2}{10}+\frac{5}{10}=\frac{7}{10}\).
2. \(\frac{1}{6}+\frac{1}{3}=\frac{1}{6}+\frac{2}{6}=\frac{3}{6}=\frac{1}{2}\).
3. \(\frac{5}{12}+\frac{1}{4}=\frac{5}{12}+\frac{3}{12}=\frac{8}{12}=\frac{2}{3}\).
4. Общий знаменатель дробей — \(90\):
   \(\frac{11}{15}-\frac{3}{10}+\frac{1}{45}=\frac{66}{90}-\frac{27}{90}+\frac{2}{90}=\frac{41}{90}\).

Ответ: 1) \(\frac{7}{10}\); 2) \(\frac{1}{2}\); 3) \(\frac{2}{3}\); 4) \(\frac{41}{90}\).