4) а) $$\frac{22p^4q^2}{99p^6q} =$$

$$\frac{22p^4q^2}{99p^6q} = \frac{22}{99} \cdot \frac{p^4}{p^6} \cdot \frac{q^2}{q} = \frac{2}{9} \cdot p^{4-6} \cdot q^{2-1} = \frac{2}{9} \cdot p^{-2} \cdot q = \frac{2q}{9p^2}$$