2.193 Выполните действие: a) +; B) +; г) 315819 + 09/09/09 ( + 19 11. 11 2 15 21 +26 3) 5+10: 42 63 24 57 60

a) $$\frac{1}{5} + \frac{1}{7} = \frac{7}{35} + \frac{5}{35} = \frac{7+5}{35} = \frac{12}{35}$$

Ответ: $$\frac{12}{35}$$

б) $$\frac{1}{3} + \frac{2}{7} = \frac{7}{21} + \frac{6}{21} = \frac{7+6}{21} = \frac{13}{21}$$

Ответ: $$\frac{13}{21}$$

в) $$\frac{3}{5} + \frac{5}{6} = \frac{18}{30} + \frac{25}{30} = \frac{18+25}{30} = \frac{43}{30} = 1\frac{13}{30}$$

Ответ: $$1\frac{13}{30}$$

г) $$\frac{8}{9} - \frac{2}{5} = \frac{40}{45} - \frac{18}{45} = \frac{40-18}{45} = \frac{22}{45}$$

Ответ: $$\frac{22}{45}$$

д) $$\frac{5}{12} + \frac{1}{6} = \frac{5}{12} + \frac{2}{12} = \frac{5+2}{12} = \frac{7}{12}$$

Ответ: $$\frac{7}{12}$$

e) $$\frac{3}{5} - \frac{4}{15} = \frac{9}{15} - \frac{4}{15} = \frac{9-4}{15} = \frac{5}{15} = \frac{1}{3}$$

Ответ: $$\frac{1}{3}$$

ж) $$\frac{19}{21} - \frac{11}{15} = \frac{19 \cdot 5}{21 \cdot 5} - \frac{11 \cdot 7}{15 \cdot 7} = \frac{95}{105} - \frac{77}{105} = \frac{95-77}{105} = \frac{18}{105} = \frac{6}{35}$$

Ответ: $$\frac{6}{35}$$

з) $$\frac{5}{42} + \frac{10}{63} = \frac{5 \cdot 3}{42 \cdot 3} + \frac{10 \cdot 2}{63 \cdot 2} = \frac{15}{126} + \frac{20}{126} = \frac{15+20}{126} = \frac{35}{126} = \frac{5}{18}$$

Ответ: $$\frac{5}{18}$$

и) $$\frac{11}{21} + \frac{2}{26} = \frac{11}{21} + \frac{1}{13} = \frac{11 \cdot 13}{21 \cdot 13} + \frac{1 \cdot 21}{13 \cdot 21} = \frac{143}{273} + \frac{21}{273} = \frac{143+21}{273} = \frac{164}{273}$$

Ответ: $$\frac{164}{273}$$

к) $$\frac{5}{24} - \frac{7}{60} = \frac{5 \cdot 5}{24 \cdot 5} - \frac{7 \cdot 2}{60 \cdot 2} = \frac{25}{120} - \frac{14}{120} = \frac{25-14}{120} = \frac{11}{120}$$

Ответ: $$\frac{11}{120}$$