№4 а) \frac{17}{25} - \frac{9}{25} + \frac{4}{25}; б) \frac{18}{19} - (\frac{8}{19} + \frac{7}{19}). а) (8-4\frac{3}{11})+2\frac{8}{11}; б) 11\frac{1}{7}-(5\frac{4}{7}+3\frac{6}{7}).

№4

1. а) $$\frac{17}{25} - \frac{9}{25} + \frac{4}{25} = \frac{17-9+4}{25} = \frac{12}{25}$$
2. б) $$\frac{18}{19} - (\frac{8}{19} + \frac{7}{19}) = \frac{18}{19} - \frac{8+7}{19} = \frac{18}{19} - \frac{15}{19} = \frac{18-15}{19} = \frac{3}{19}$$
3. а) $$(8-4\frac{3}{11})+2\frac{8}{11} = (8 - \frac{4 \cdot 11 + 3}{11}) + \frac{2 \cdot 11 + 8}{11} = (8 - \frac{47}{11}) + \frac{30}{11} = \frac{8 \cdot 11 - 47}{11} + \frac{30}{11} = \frac{88 - 47 + 30}{11} = \frac{71}{11} = 6\frac{5}{11}$$
4. б) $$11\frac{1}{7}-(5\frac{4}{7}+3\frac{6}{7}) = \frac{11 \cdot 7 + 1}{7} - (\frac{5 \cdot 7 + 4}{7} + \frac{3 \cdot 7 + 6}{7}) = \frac{78}{7} - (\frac{39}{7} + \frac{27}{7}) = \frac{78}{7} - \frac{39 + 27}{7} = \frac{78 - 66}{7} = \frac{12}{7} = 1\frac{5}{7}$$

Ответ: а) $$\frac{12}{25}$$; б) $$\frac{3}{19}$$; а) $$6\frac{5}{11}$$; б) $$1\frac{5}{7}$$