135. Выполните действия: a) $$(1\frac{3}{5}+2\frac{1}{5}):1\frac{9}{10}+(1\frac{7}{10}-\frac{4}{5}):\frac{3}{7}$$; б) $$6\frac{3}{8}\cdot 1\frac{7}{17}-2\frac{3}{8}:1\frac{1}{4}+\frac{2}{5}$$:

a) $$(1\frac{3}{5}+2\frac{1}{5}):1\frac{9}{10}+(1\frac{7}{10}-\frac{4}{5}):\frac{3}{7}$$;

1) $$1\frac{3}{5}+2\frac{1}{5}=\frac{8}{5}+ \frac{11}{5}=\frac{19}{5}$$;

2) $$1\frac{9}{10}=\frac{19}{10}$$;

3) $$\frac{19}{5}:\frac{19}{10}=\frac{19}{5} \cdot \frac{10}{19}=\frac{19\cdot 10}{5\cdot 19}=\frac{10}{5}=2$$;

4) $$1\frac{7}{10}-\frac{4}{5}=\frac{17}{10}-\frac{4}{5}=\frac{17}{10}-\frac{4 \cdot 2}{5 \cdot 2}=\frac{17}{10}-\frac{8}{10}=\frac{9}{10}$$;

5) $$\frac{9}{10}:\frac{3}{7}=\frac{9}{10} \cdot \frac{7}{3}=\frac{9 \cdot 7}{10 \cdot 3}=\frac{3 \cdot 7}{10}=\frac{21}{10}=2\frac{1}{10}$$;

6) $$2+2\frac{1}{10}=4\frac{1}{10}$$.

Ответ: $$4\frac{1}{10}$$

б) $$6\frac{3}{8}\cdot 1\frac{7}{17}-2\frac{3}{8}:1\frac{1}{4}+\frac{2}{5}$$;

1) $$6\frac{3}{8}\cdot 1\frac{7}{17}=\frac{51}{8} \cdot \frac{24}{17}=\frac{51 \cdot 24}{8 \cdot 17}=\frac{3 \cdot 3}{1 \cdot 1} = 9$$;

2) $$2\frac{3}{8}:1\frac{1}{4}=\frac{19}{8}:\frac{5}{4}=\frac{19}{8} \cdot \frac{4}{5}=\frac{19 \cdot 4}{8 \cdot 5}=\frac{19}{2 \cdot 5}=\frac{19}{10}=1\frac{9}{10}$$;

3) $$9-1\frac{9}{10}=8\frac{10}{10}-1\frac{9}{10}=7\frac{1}{10}$$;

4) $$7\frac{1}{10}+\frac{2}{5}=7\frac{1}{10}+\frac{2 \cdot 2}{5 \cdot 2}=7\frac{1}{10}+ \frac{4}{10}=7\frac{5}{10}=7\frac{1}{2}$$.

Ответ: $$7\frac{1}{2}$$