Subtract$2\surd 45$ from$4\surd 20.$

What is the simplified value of $\left[\left(\sqrt{9}+\sqrt{7}\right)÷\left(\sqrt{9}-\sqrt{7}\right)\right]$?

What is the simplified value of $\left[\left(\sqrt{41}+\sqrt{7}\right) ÷\left(\sqrt{41}-\sqrt{7}\right)\right]?$

Which of the following statement is true?

I. $\sqrt[9]{6}>\sqrt[18]{5}$

II. $\sqrt[4]{7}>\sqrt[6]{11}$ 

Which of the following relation(s) is/are true? 

$$\begin{gathered} I. \sqrt{2}>\sqrt[3]{3} \\ II. \sqrt[3]{3}>\sqrt{2} \\ III. \sqrt{2}=\sqrt[3]{3} \end{gathered}$$

$1$. $\sqrt{676}+\sqrt{6.76}+\sqrt{0.0676}=27.76$

$2$. $\sqrt{339+\sqrt{36}+\sqrt{49}+\sqrt{81}}=19$