4) $$20m^6 \cdot \frac{3x^3}{5m^9} = \frac{20m^6 \cdot 3x^3}{5m^9} = \frac{60m^6x^3}{5m^9} = \frac{12x^3}{m^3}$$
Ответ: $$\frac{12x^3}{m^3}$$