4 6p mn³ ( -m²n) : 24p

4) $$ (-\frac{6p}{m^2n}) \cdot \frac{mn^3}{24p} = - \frac{6p \cdot mn^3}{m^2n \cdot 24p} = - \frac{6}{24} \cdot \frac{p}{p} \cdot \frac{m}{m^2} \cdot \frac{n^3}{n} = - \frac{1}{4} \cdot 1 \cdot \frac{1}{m} \cdot n^2 = - \frac{n^2}{4m} $$

Ответ: $$\frac{-n^2}{4m}$$