10) $$\frac{c^5 \cdot c^8}{c^4 \cdot c^{10}} = \frac{c^{5+8}}{c^{4+10}} = \frac{c^{13}}{c^{14}} = c^{13-14} = c^{-1} = \frac{1}{c}$$.
Ответ: $$\frac{1}{c}$$