Решение:

б) $$\left(\frac{a}{m^2} + \frac{a^2}{m^3}\right) : \left(\frac{m^2}{a^2} + \frac{m}{a}\right) =$$ $$\left(\frac{am + a^2}{m^3}\right) : \left(\frac{m^2 + ma}{a^2}\right) =$$ $$\frac{a(m + a)}{m^3} \cdot \frac{a^2}{m(m + a)} =$$ $$\frac{a^3}{m^4}$$

Ответ: $$\frac{a^3}{m^4}$$