Начнем с примера 4: \[1\frac{2}{7} \cdot \frac{2}{9} = \frac{9}{7} \cdot \frac{2}{9} = \frac{9 \cdot 2}{7 \cdot 9} = \frac{18}{63} = \frac{2}{7}\]
Ответ: \(\frac{2}{7}\)