2. Вычислите: a) \(\frac{5}{6}+(-\frac{7}{12})\); б) \(-\frac{3}{10}-\frac{1}{15}\); в) \(-\frac{3}{5}\cdot \frac{5}{9}\); г) \(\frac{8}{21}:(-\frac{4}{7})\)

2. Вычислите:

a) \(\frac{5}{6}+(-\frac{7}{12}) = \frac{5}{6} - \frac{7}{12} = \frac{5 \cdot 2}{6 \cdot 2} - \frac{7}{12} = \frac{10}{12} - \frac{7}{12} = \frac{10-7}{12} = \frac{3}{12} = \frac{1}{4}\)

Ответ: \(\frac{1}{4}\)

б) \(-\frac{3}{10}-\frac{1}{15} = -\frac{3 \cdot 3}{10 \cdot 3} - \frac{1 \cdot 2}{15 \cdot 2} = -\frac{9}{30} - \frac{2}{30} = -\frac{9+2}{30} = -\frac{11}{30}\)

Ответ: \(-\frac{11}{30}\)

в) \(-\frac{3}{5}\cdot \frac{5}{9} = -\frac{3 \cdot 5}{5 \cdot 9} = -\frac{15}{45} = -\frac{1}{3}\)

Ответ: \(-\frac{1}{3}\)

г) \(\frac{8}{21}:(-\frac{4}{7}) = \frac{8}{21} \cdot (-\frac{7}{4}) = -\frac{8 \cdot 7}{21 \cdot 4} = -\frac{56}{84} = -\frac{2}{3}\)

Ответ: \(-\frac{2}{3}\)