Решим данные примеры:
a) $$7\frac{8}{9} - 3\frac{5}{9} = (7 - 3) + (\frac{8}{9} - \frac{5}{9}) = 4 + \frac{3}{9} = 4\frac{1}{3}$$.
б) $$5\frac{5}{12} + 2\frac{1}{12} = (5 + 2) + (\frac{5}{12} + \frac{1}{12}) = 7 + \frac{6}{12} = 7\frac{1}{2}$$.
в) $$29\frac{11}{21} - 29\frac{5}{21} = (29 - 29) + (\frac{11}{21} - \frac{5}{21}) = 0 + \frac{6}{21} = \frac{2}{7}$$.
г) $$6\frac{3}{10} + 7\frac{5}{10} = (6 + 7) + (\frac{3}{10} + \frac{5}{10}) = 13 + \frac{8}{10} = 13\frac{4}{5}$$.
Ответ: a) $$4\frac{1}{3}$$; б) $$7\frac{1}{2}$$; в) $$\frac{2}{7}$$; г) $$13\frac{4}{5}$$.