11. Сложите дроби: а) $$\frac{7}{10} + \frac{1}{20}$$; б) $$\frac{7}{12} + \frac{1}{4}$$; в) $$\frac{1}{15} + \frac{2}{5}$$; г) $$\frac{5}{9} + \frac{1}{3}$$; д) $$2 + \frac{4}{15}$$; е) $$\frac{7}{18} + \frac{1}{15}$$; ё) $$1 + \frac{3}{7}$$; ж) $$\frac{5}{6} + \frac{5}{18}$$

Решение:

1. \[ \frac{7}{10} + \frac{1}{20} = \frac{14}{20} + \frac{1}{20} = \frac{15}{20} = \frac{3}{4} \]
2. \[ \frac{7}{12} + \frac{1}{4} = \frac{7}{12} + \frac{3}{12} = \frac{10}{12} = \frac{5}{6} \]
3. \[ \frac{1}{15} + \frac{2}{5} = \frac{1}{15} + \frac{6}{15} = \frac{7}{15} \]
4. \[ \frac{5}{9} + \frac{1}{3} = \frac{5}{9} + \frac{3}{9} = \frac{8}{9} \]
5. \[ 2 + \frac{4}{15} = \frac{30}{15} + \frac{4}{15} = \frac{34}{15} \]
6. \[ \frac{7}{18} + \frac{1}{15} = \frac{35}{90} + \frac{6}{90} = \frac{41}{90} \]
7. \[ 1 + \frac{3}{7} = \frac{7}{7} + \frac{3}{7} = \frac{10}{7} \]
8. \[ \frac{5}{6} + \frac{5}{18} = \frac{15}{18} + \frac{5}{18} = \frac{20}{18} = \frac{10}{9} \]