1. Найдите значение выражения: a) 2 - 1-; б) 4 +3-; в) - (1+2-).

a) $$2 \frac{3}{5} - 1 \frac{1}{6} = \frac{13}{5} - \frac{7}{6} = \frac{13 \cdot 6 - 7 \cdot 5}{30} = \frac{78 - 35}{30} = \frac{43}{30} = 1 \frac{13}{30}$$

б) $$4 \frac{5}{6} + 3 \frac{2}{5} = \frac{29}{6} + \frac{17}{5} = \frac{29 \cdot 5 + 17 \cdot 6}{30} = \frac{145 + 102}{30} = \frac{247}{30} = 8 \frac{7}{30}$$

в) $$\frac{5}{12} - (1 \frac{5}{8} + 2 \frac{1}{24}) = \frac{5}{12} - (\frac{13}{8} + \frac{49}{24}) = \frac{5}{12} - (\frac{13 \cdot 3 + 49}{24}) = \frac{5}{12} - \frac{39 + 49}{24} = \frac{5}{12} - \frac{88}{24} = \frac{5 \cdot 2 - 88}{24} = \frac{10 - 88}{24} = \frac{-78}{24} = -\frac{13}{4} = -3 \frac{1}{4}$$

Ответ: a) $$1 \frac{13}{30}$$; б) $$8 \frac{7}{30}$$; в) $$-3 \frac{1}{4}$$