4. Вычислите частное: $$\frac{8x}{21y^2} : \frac{6x^2}{7y}$$

$$\frac{8x}{21y^2} : \frac{6x^2}{7y} = \frac{8x}{21y^2} \cdot \frac{7y}{6x^2} = \frac{8x \cdot 7y}{21y^2 \cdot 6x^2} = \frac{56xy}{126x^2y^2} = \frac{28 \cdot 2 xy}{28 \cdot 4.5 xxyy} = \frac{4}{9xy}$$ Ответ: Б) $$\frac{4}{9xy}$$