Ответ:

  1. \(3\cdot\frac{2}{13}=\frac{6}{13}\).
  2. \(12\cdot\frac{5}{6}=2\cdot5=10\).
  3. \(7\cdot\frac{15}{28}=\frac{15}{4}=3\frac{3}{4}\).
  4. \(\frac{10}{27}\cdot18=10\cdot\frac{2}{3}=\frac{20}{3}=6\frac{2}{3}\).

Ответ: 1) 6/13; 2) 10; 3) 3 3/4; 4) 6 2/3.