Ответ:

  1. Сократим множители: \(\frac{2.4}{4.8}\cdot\frac{12.3}{6.3}\cdot\frac{3.5}{21}=\frac{1}{2}\cdot\frac{41}{21}\cdot\frac{1}{6}=\frac{41}{252}\).
  2. \(\frac{0.9\cdot5.4\cdot2.8}{1.8\cdot2.7\cdot16.8}=\frac{0.9}{1.8}\cdot\frac{5.4}{2.7}\cdot\frac{2.8}{16.8}=\frac{1}{2}\cdot2\cdot\frac{1}{6}=\frac{1}{6}\).
  3. \(\frac{3.2\cdot8.1\cdot5.6}{4.8\cdot0.4\cdot2.7}=\frac{3.2}{0.4}\cdot\frac{8.1}{2.7}\cdot\frac{5.6}{4.8}=8\cdot3\cdot\frac{7}{6}=28\).

Ответ: а) \(\frac{41}{252}\); б) \(\frac{1}{6}\); в) \(28\).