4. Найдите значение выражений. a) 3/15 + 9/15 - 4/15 б) 10 19/36 - (4 13/36 + 3 7/36) в) (12 3/18 - 7 11/18) + 3 15/18

a) $$\frac{3}{15} + \frac{9}{15} - \frac{4}{15} = \frac{3 + 9 - 4}{15} = \frac{12 - 4}{15} = \frac{8}{15}$$ б) $$10 \frac{19}{36} - (4 \frac{13}{36} + 3 \frac{7}{36}) = 10 \frac{19}{36} - (7 \frac{20}{36}) = 10 \frac{19}{36} - 7 \frac{5}{9} = 10 \frac{19}{36} - 7 \frac{20}{36} = (10 - 7) + (\frac{19}{36} - \frac{20}{36}) = 3 - \frac{1}{36} = 2 \frac{36}{36} - \frac{1}{36} = 2 \frac{35}{36}$$ в) $$(12 \frac{3}{18} - 7 \frac{11}{18}) + 3 \frac{15}{18} = (12 \frac{3}{18} - 7 \frac{11}{18}) + 3 \frac{15}{18} = (11 \frac{21}{18} - 7 \frac{11}{18}) + 3 \frac{15}{18} = 4 \frac{10}{18} + 3 \frac{15}{18} = 7 \frac{25}{18} = 7 + \frac{25}{18} = 7 + 1 \frac{7}{18} = 8 \frac{7}{18}$$