The simplest value of $\frac{1}{\sqrt{2}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{4}}+\frac{1}{\sqrt{4}+\sqrt{5}}+\frac{1}{\sqrt{5}+\sqrt{6}}$ is _____

If $\text{'}+\text{'}$ means $\text{'}÷\text{'}$, $\text{'}\times \text{'}$ means $\text{'}–\text{'}$, $\text{'}÷\text{'}$ means $\text{'}\times \text{'}$ and $\text{'}–\text{'}$ means $\text{'}+\text{'}$, what will be the value of the following expression?

$9+3÷4-8\times 2=?$

If $y+\frac{1}{z}=1, x+\frac{1}{y}=1$ then, find the value of $xyz$.