2. Найдите значение выражения: 11 A) - - 4 1 +; 30 15 20' 7 Б) 9-5; 11' 4 B) 5+2; 9 5 12

A) $$\frac{11}{30} - \frac{4}{15} + \frac{1}{20} = \frac{11}{30} - \frac{4 \cdot 2}{15 \cdot 2} + \frac{1 \cdot 1.5}{20 \cdot 1.5} = \frac{11}{30} - \frac{8}{30} + \frac{1.5}{30} = \frac{11 - 8 + 1.5}{30} = \frac{4.5}{30} = \frac{45}{300} = \frac{3}{20} = 0.15$$

Б) $$9 - 5\frac{7}{11} = 8\frac{11}{11} - 5\frac{7}{11} = (8 - 5) + (\frac{11}{11} - \frac{7}{11}) = 3 + \frac{4}{11} = 3\frac{4}{11}$$

B) $$5\frac{4}{9} + 2\frac{5}{12} = 5 + \frac{4}{9} + 2 + \frac{5}{12} = (5+2) + (\frac{4}{9} + \frac{5}{12}) = 7 + (\frac{4 \cdot 4}{9 \cdot 4} + \frac{5 \cdot 3}{12 \cdot 3}) = 7 + (\frac{16}{36} + \frac{15}{36}) = 7 + \frac{31}{36} = 7\frac{31}{36}$$

Ответ: А) 0.15; Б) $$3\frac{4}{11}$$; В) $$7\frac{31}{36}$$