2) \(3 \cdot \frac{7}{9}\) 4) \(\frac{5}{6} \cdot (-\frac{3}{7})\) 6) \(-\frac{34}{35} \cdot \frac{45}{51}\)

Решение:

• 2) \(3 \cdot \frac{7}{9} = \frac{3 \cdot 7}{9} = \frac{21}{9} = \frac{7}{3}\)
• 4) \(\frac{5}{6} \cdot (-\frac{3}{7}) = -\frac{5 \cdot 3}{6 \cdot 7} = -\frac{15}{42} = -\frac{5}{14}\)
• 6) \(-\frac{34}{35} \cdot \frac{45}{51}\)
• Сокращаем 34 и 51 на 17: \(34/17 = 2\), \(51/17 = 3\)
• Сокращаем 45 и 35 на 5: \(45/5 = 9\), \(35/5 = 7\)
• \(-\frac{2 \cdot 9}{7 \cdot 3} = -\frac{18}{21} = -\frac{6}{7}\)

Ответ: 7/3; -5/14; -6/7.