\[\boxed{\mathbf{335\ (335).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \frac{2}{7} \cdot \frac{3}{5} = \frac{2 \cdot 3}{7 \cdot 5} = \frac{6}{35}\]
\[3)\ \frac{4}{7} \cdot \frac{7}{9} = \frac{4 \cdot 7}{7 \cdot 9} = \frac{4}{9}\]