1. Найдите значение выражения: 10 4 3 a) + - + ; 11 11 11 7 4 б) 2- +3-; 15 15 5 8 в) 4- +3-; 9 9 3 г) 6-3-; 8 12 7 д) 7- -5-; 13 13 6 11 е) 5- -1-. 15 15

a) $$\frac{10}{11} + \frac{4}{11} + \frac{3}{11} = \frac{10+4+3}{11} = \frac{17}{11} = 1\frac{6}{11}$$

б) $$2\frac{7}{15} + 3\frac{4}{15} = 2 + \frac{7}{15} + 3 + \frac{4}{15} = (2 + 3) + (\frac{7}{15} + \frac{4}{15}) = 5 + \frac{7+4}{15} = 5 + \frac{11}{15} = 5\frac{11}{15}$$

в) $$4\frac{5}{9} + 3\frac{8}{9} = 4 + \frac{5}{9} + 3 + \frac{8}{9} = (4 + 3) + (\frac{5}{9} + \frac{8}{9}) = 7 + \frac{5+8}{9} = 7 + \frac{13}{9} = 7 + 1\frac{4}{9} = 8\frac{4}{9}$$

г) $$6 - 3\frac{3}{8} = 6 - (3 + \frac{3}{8}) = (6 - 3) - \frac{3}{8} = 3 - \frac{3}{8} = 2\frac{8}{8} - \frac{3}{8} = 2\frac{8-3}{8} = 2\frac{5}{8}$$

д) $$7\frac{12}{13} - 5\frac{7}{13} = 7 + \frac{12}{13} - (5 + \frac{7}{13}) = (7 - 5) + (\frac{12}{13} - \frac{7}{13}) = 2 + \frac{12-7}{13} = 2 + \frac{5}{13} = 2\frac{5}{13}$$

e) $$5\frac{6}{15} - 1\frac{11}{15} = 5 + \frac{6}{15} - (1 + \frac{11}{15}) = (5 - 1) + (\frac{6}{15} - \frac{11}{15}) = 4 + \frac{6-11}{15} = 4 - \frac{5}{15} = 3\frac{15}{15} - \frac{5}{15} = 3\frac{15-5}{15} = 3\frac{10}{15} = 3\frac{2}{3}$$

Ответ: a) $$1\frac{6}{11}$$, б) $$5\frac{11}{15}$$, в) $$8\frac{4}{9}$$, г) $$2\frac{5}{8}$$, д) $$2\frac{5}{13}$$, e) $$3\frac{2}{3}$$