若正项等比数列 $\left\{a_{n}\right\}$ 的公比 $q \neq 1$, 且 $a_{3}, a_{5}, a_{6}$ 成等差数列, 则 $\frac{a_{3}+a_{5}+a_{6}}{}$ 等于 $(\quad)$
$a_{3}+a_{6}=2 a_{5}, \therefore a_{1} q^{2}+a_{1} q^{5}=2 a_{1} q^{4}$,

$\therefore q^{3}-2 q^{2}+1=0, \quad \therefore(q-1)\left(q^{2}-q-1\right)=0(q \neq 1)$,

$\therefore q^{2}-q-1=0, \quad \therefore q=\frac{\sqrt{5}+1}{2}\left(q=\frac{1-\sqrt{5}}{2}<0\right.$ 舍 $)$

$\therefore \frac{a_{3}+a_{5}}{a_{4}+a_{6}}=\frac{1}{q}=\frac{\sqrt{5}-1}{2}$.