а) $$rac{4}{7} : rac{16}{49} = rac{4}{7} \cdot \frac{49}{16} = \frac{4 \cdot 49}{7 \cdot 16} = \frac{1 \cdot 7}{1 \cdot 4} = \frac{7}{4} = 1\frac{3}{4}$$
Ответ: $$1\frac{3}{4}$$