3) 4 2/7 - 1 4/9 ;

3) $$4 \frac{2}{7} - 1 \frac{4}{9} = (4 - 1) + (\frac{2}{7} - \frac{4}{9}) = 3 + (\frac{2 \cdot 9}{7 \cdot 9} - \frac{4 \cdot 7}{9 \cdot 7}) = 3 + (\frac{18}{63} - \frac{28}{63}) = 3 - \frac{10}{63} = 2 \frac{63}{63} - \frac{10}{63} = 2 \frac{53}{63}$$

Ответ: $$2 \frac{53}{63}$$