13. 88u6c9 154u5c11

$$\frac{88u^6c^9}{154u^5c^{11}} = \frac{4 \cdot 22 u^6 c^9}{7 \cdot 22 u^5 c^{11}} = \frac{4u}{7c^2}$$ Ответ: $$\frac{4u}{7c^2}$$