99 q.q 30 39) y 20 y 20 = y10. yoy10

39) $$\frac{y^{20} \cdot y^{30}}{y^{10} \cdot y^0 \cdot y^{10}} = \frac{y^{20+30}}{y^{10+0+10}} = \frac{y^{50}}{y^{20}} = y^{50-20} = y^{30}$$

Ответ: $$y^{30}$$