11 Вычислите:

а) \( \frac{1}{3} + \frac{5}{6} = \frac{2}{6} + \frac{5}{6} = \frac{7}{6} \); б) \( \frac{5}{6} - \frac{1}{2} = \frac{5}{6} - \frac{3}{6} = \frac{2}{6} = \frac{1}{3} \); в) \( \frac{9}{10} - \frac{4}{5} = \frac{9}{10} - \frac{8}{10} = \frac{1}{10} \); г) \( \frac{5}{6} - \frac{5}{12} = \frac{10}{12} - \frac{5}{12} = \frac{5}{12} \); д) \( \frac{11}{18} + \frac{1}{6} = \frac{11}{18} + \frac{3}{18} = \frac{14}{18} = \frac{7}{9} \); е) \( \frac{5}{12} + \frac{3}{4} = \frac{5}{12} + \frac{9}{12} = \frac{14}{12} = \frac{7}{6} \); ж) \( \frac{4}{5} - \frac{7}{15} = \frac{12}{15} - \frac{7}{15} = \frac{5}{15} = \frac{1}{3} \); з) \( \frac{11}{21} + \frac{3}{7} = \frac{11}{21} + \frac{9}{21} = \frac{20}{21} \).