$\frac{4.2 \times 4.2 - 1.9 \times 1.9}{2.3 \times 6.1} = ?$

If $x = \sqrt{a \sqrt[3]{b \sqrt{a \sqrt[3]{b \dots \infty}}}},$ then the value of $x$ is:

Manmohan spends $\frac{1}{5}$ part of his money as pocket money and $\frac{4}{5}$ of the remainder in other affairs. If he is left with $Rs.\, 48$ per month,what is his monthly income? (in $Rs.$)

$2+\sqrt{2}+\frac{1}{2+\sqrt{2}}+\frac{1}{\sqrt{2}-2}=?$

$\frac{3}{48}$ is what part of $\frac{1}{12}$?

Which of the following statement$(s)$ is/are $TRUE$?
$I.$ $\frac{2}{3 \sqrt{5}} < \frac{3}{2 \sqrt{5}} < \frac{5}{4 \sqrt{3}}$
$II.$ $\frac{3}{2 \sqrt{5}} < \frac{2}{3 \sqrt{3}} < \frac{7}{4 \sqrt{5}}$