4. Выполните действия а) $$\frac{3}{4} - \frac{1}{6}$$ б) $$\frac{11}{12} + \frac{9}{10}$$ в) $$\frac{3}{7} \cdot \frac{7}{9}$$ г) $$\frac{2}{3} : \frac{2}{7}$$ д) 6$$\frac{5}{6}+2\frac{3}{8}$$ е) 3$$\frac{4}{7}-2\frac{3}{5}$$ ж) 2$$\frac{1}{7} \cdot 3\frac{1}{9}$$ з) 3$$\frac{3}{5}:2\frac{7}{10}$$

а) $$\frac{3}{4} - \frac{1}{6}$$ = $$\frac{3 \cdot 3}{4 \cdot 3} - \frac{1 \cdot 2}{6 \cdot 2}$$ = $$\frac{9}{12} - \frac{2}{12}$$ = $$\frac{9-2}{12}$$ = $$\frac{7}{12}$$

б) $$\frac{11}{12} + \frac{9}{10}$$ = $$\frac{11 \cdot 5}{12 \cdot 5} + \frac{9 \cdot 6}{10 \cdot 6}$$ = $$\frac{55}{60} + \frac{54}{60}$$ = $$\frac{55+54}{60}$$ = $$\frac{109}{60}$$ = 1$$\frac{49}{60}$$

в) $$\frac{3}{7} \cdot \frac{7}{9}$$ = $$\frac{3 \times 7}{7 \times 9}$$ = $$\frac{21}{63}$$ = $$\frac{3 \times 7}{9 \times 7}$$ = $$\frac{3}{9}$$ = $$\frac{1 \times 3}{3 \times 3}$$ = $$\frac{1}{3}$$

г) $$\frac{2}{3} : \frac{2}{7}$$ = $$\frac{2}{3} \times \frac{7}{2}$$ = $$\frac{2 \times 7}{3 \times 2}$$ = $$\frac{14}{6}$$ = $$\frac{7 \times 2}{3 \times 2}$$ = $$\frac{7}{3}$$ = 2$$\frac{1}{3}$$

д) 6$$\frac{5}{6}+2\frac{3}{8}$$ = 6 + 2 + $$\frac{5}{6} + \frac{3}{8}$$ = 8 + $$\frac{5 \cdot 4}{6 \cdot 4} + \frac{3 \cdot 3}{8 \cdot 3}$$ = 8 + $$\frac{20}{24} + \frac{9}{24}$$ = 8 + $$\frac{29}{24}$$ = 8 + 1$$\frac{5}{24}$$ = 9$$\frac{5}{24}$$

е) 3$$\frac{4}{7}-2\frac{3}{5}$$ = 3 - 2 + $$\frac{4}{7} - \frac{3}{5}$$ = 1 + $$\frac{4 \cdot 5}{7 \cdot 5} - \frac{3 \cdot 7}{5 \cdot 7}$$ = 1 + $$\frac{20}{35} - \frac{21}{35}$$ = 1 - $$\frac{1}{35}$$ = $$\frac{35}{35} - \frac{1}{35}$$ = $$\frac{34}{35}$$

ж) 2$$\frac{1}{7} \cdot 3\frac{1}{9}$$ = $$\frac{15}{7} \cdot \frac{28}{9}$$ = $$\frac{15 \times 28}{7 \times 9}$$ = $$\frac{15 \times 4 \times 7}{7 \times 9}$$ = $$\frac{15 \times 4}{9}$$ = $$\frac{5 \times 3 \times 4}{3 \times 3}$$ = $$\frac{5 \times 4}{3}$$ = $$\frac{20}{3}$$ = 6$$\frac{2}{3}$$

з) 3$$\frac{3}{5}:2\frac{7}{10}$$ = $$\frac{18}{5} : \frac{27}{10}$$ = $$\frac{18}{5} \times \frac{10}{27}$$ = $$\frac{18 \times 10}{5 \times 27}$$ = $$\frac{2 \times 9 \times 2 \times 5}{5 \times 3 \times 9}$$ = $$\frac{2 \times 2}{3}$$ = $$\frac{4}{3}$$ = 1$$\frac{1}{3}$$

Ответ: а) $$\frac{7}{12}$$; б) 1$$\frac{49}{60}$$; в) $$\frac{1}{3}$$; г) 2$$\frac{1}{3}$$; д) 9$$\frac{5}{24}$$; е) $$\frac{34}{35}$$; ж) 6$$\frac{2}{3}$$; з) 1$$\frac{1}{3}$$