1.Выполните действия: а) 2 + 3; 6) 12-9 в) 1*3; г)5:1

a) $$2\frac{3}{4} + 3\frac{4}{7} = \frac{11}{4} + \frac{25}{7} = \frac{11 \cdot 7 + 25 \cdot 4}{28} = \frac{77 + 100}{28} = \frac{177}{28} = 6\frac{9}{28}$$

б) $$12\frac{5}{12} - 9\frac{13}{18} = \frac{149}{12} - \frac{175}{18} = \frac{149 \cdot 3 - 175 \cdot 2}{36} = \frac{447 - 350}{36} = \frac{97}{36} = 2\frac{25}{36}$$

в) $$1\frac{5}{8} \cdot 3\frac{5}{9} = \frac{13}{8} \cdot \frac{32}{9} = \frac{13 \cdot 32}{8 \cdot 9} = \frac{13 \cdot 4}{1 \cdot 9} = \frac{52}{9} = 5\frac{7}{9}$$

г) $$5\frac{3}{4} : 1\frac{5}{8} = \frac{23}{4} : \frac{13}{8} = \frac{23}{4} \cdot \frac{8}{13} = \frac{23 \cdot 8}{4 \cdot 13} = \frac{23 \cdot 2}{1 \cdot 13} = \frac{46}{13} = 3\frac{7}{13}$$

Ответ: а) $$6\frac{9}{28}$$; б) $$2\frac{25}{36}$$; в) $$5\frac{7}{9}$$; г) $$3\frac{7}{13}$$