Ответ:

  1. \(4\cdot\frac{4}{21}=\frac{16}{21}\).
  2. Преобразуем смешанное число: \(6\cdot1\frac{7}{18}=6\cdot\frac{25}{18}=\frac{25}{3}=8\frac{1}{3}\).
  3. \(\frac{5}{14}\cdot28=5\cdot2=10\).
  4. \(5\frac{3}{5}\cdot\frac{3}{7}=\frac{28}{5}\cdot\frac{3}{7}=\frac{12}{5}=2\frac{2}{5}\).
  5. \(2\frac{2}{13}\cdot1\frac{9}{16}=\frac{28}{13}\cdot\frac{25}{16}=\frac{175}{52}=3\frac{19}{52}\).
  6. \(1\frac{7}{8}\cdot1\frac{1}{15}\cdot\frac{7}{16}=\frac{15}{8}\cdot\frac{16}{15}\cdot\frac{7}{16}=\frac{7}{8}\).

Ответ: 1) \(\frac{16}{21}\); 2) \(8\frac{1}{3}\); 3) 10; 4) \(2\frac{2}{5}\); 5) \(3\frac{19}{52}\); 6) \(\frac{7}{8}\).