e) 3a^2/b^2 * b^3 ;

e) $$\frac{3a^2}{b^2} \cdot b^3 = \frac{3a^2}{b^2} \cdot \frac{b^3}{1} = \frac{3a^2b^3}{b^2} = 3a^2b$$

Ответ: $$3a^2b$$