Найдите значение выражения: a) $$3\frac{4}{4}+2\frac{4}{7}$$; б) $$2\frac{4}{9}-1\frac{5}{6}$$; в) $$7\frac{11}{15}+(3\frac{1}{30}-1\frac{9}{20})$$.

а) $$3\frac{4}{4}+2\frac{4}{7} = 3 + 1 + 2\frac{4}{7} = 4 + 2\frac{4}{7} = 6\frac{4}{7}$$. Ответ: $$6\frac{4}{7}$$.

б) $$2\frac{4}{9}-1\frac{5}{6} = \frac{22}{9}-\frac{11}{6} = \frac{44}{18}-\frac{33}{18} = \frac{11}{18}$$. Ответ: $$rac{11}{18}$$.

в) $$7\frac{11}{15}+(3\frac{1}{30}-1\frac{9}{20}) = 7\frac{11}{15}+(3\frac{2}{60}-1\frac{27}{60}) = 7\frac{11}{15}+(2\frac{62}{60}-1\frac{27}{60}) = 7\frac{11}{15}+1\frac{35}{60} = 7\frac{11}{15}+1\frac{7}{12} = 7\frac{44}{60}+1\frac{35}{60} = 8\frac{79}{60} = 9\frac{19}{60}$$. Ответ: $$9\frac{19}{60}$$.