ВАРИАНТ 2. 1. Найдите значение выражения: a)-5/11 + 3/11 + 7/11; б) 9/19 * (13/18 - 3/19); в) 10 4/21 - (4 10/21 + 3 19/21).

ВАРИАНТ 2. 1. Найдите значение выражения: a) $$\frac{5}{11} + \frac{3}{11} + \frac{7}{11} = \frac{5+3+7}{11} = \frac{15}{11} = 1\frac{4}{11}.$$ Ответ: $$1\frac{4}{11}$$ б) $$9\frac{13}{19} + (8\frac{18}{19} - 3\frac{15}{19}) = \frac{9*19 + 13}{19} + (\frac{8*19 + 18}{19} - \frac{3*19 + 15}{19}) = \frac{171 + 13}{19} + (\frac{152 + 18}{19} - \frac{57 + 15}{19}) = \frac{184}{19} + (\frac{170}{19} - \frac{72}{19}) = \frac{184}{19} + \frac{170 - 72}{19} = \frac{184}{19} + \frac{98}{19} = \frac{184 + 98}{19} = \frac{282}{19} = 14\frac{16}{19}.$$ Ответ: $$14\frac{16}{19}$$ в) $$10\frac{4}{21} - (4\frac{10}{21} + 3\frac{19}{21}) = \frac{10*21 + 4}{21} - (\frac{4*21 + 10}{21} + \frac{3*21 + 19}{21}) = \frac{210 + 4}{21} - (\frac{84 + 10}{21} + \frac{63 + 19}{21}) = \frac{214}{21} - (\frac{94}{21} + \frac{82}{21}) = \frac{214}{21} - \frac{94 + 82}{21} = \frac{214}{21} - \frac{176}{21} = \frac{214 - 176}{21} = \frac{38}{21} = 1\frac{17}{21}.$$ Ответ: $$1\frac{17}{21}$$