35s3t48u3 14u2 20st2

$$\frac{35s^3t^4}{14u^2} \cdot \frac{8u^3}{20st^2} = \frac{35 \cdot 8 \cdot s^3 \cdot t^4 \cdot u^3}{14 \cdot 20 \cdot u^2 \cdot s \cdot t^2} = \frac{280s^3t^4u^3}{280u^2st^2} = s^{3-1}t^{4-2}u^{3-2} = s^2t^2u$$ Ответ: $$s^2t^2u$$