2. Выполните действия: a) $$\frac{3}{7} + \frac{5}{14}$$; б) $$\frac{8}{9} - \frac{7}{12}$$; в) $$\frac{11}{50} - \frac{3}{25} + \frac{1}{20}$$.

2. a) $$\frac{3}{7} + \frac{5}{14} = \frac{3 \cdot 2}{7 \cdot 2} + \frac{5}{14} = \frac{6}{14} + \frac{5}{14} = \frac{11}{14}$$ б) $$\frac{8}{9} - \frac{7}{12} = \frac{8 \cdot 4}{9 \cdot 4} - \frac{7 \cdot 3}{12 \cdot 3} = \frac{32}{36} - \frac{21}{36} = \frac{11}{36}$$ в) $$\frac{11}{50} - \frac{3}{25} + \frac{1}{20} = \frac{11 \cdot 2}{50 \cdot 2} - \frac{3 \cdot 4}{25 \cdot 4} + \frac{1 \cdot 5}{20 \cdot 5} = \frac{22}{100} - \frac{12}{100} + \frac{5}{100} = \frac{22 - 12 + 5}{100} = \frac{15}{100} = \frac{3}{20}$$ Ответ: а) $$\frac{11}{14}$$, б) $$\frac{11}{36}$$, в) $$\frac{3}{20}$$