3) (4,5m²)(1/3 m²x);

3) $$(4,5m^2)(\frac{1}{3} m^2x) = 4,5 \cdot \frac{1}{3} \cdot m^2 \cdot m^2 \cdot x = \frac{4,5}{3}m^4x = 1,5m^4x$$

Ответ: $$1,5m^4x$$