$\sqrt{1.5625} = ?$

$\sqrt{\frac{48.4}{0.289}}$ is equal to

If $\sqrt{x} + \sqrt{441} = 0.02$,then the value of $x$ is

In the following questions,two equations numbered $I$ and $II$ are given. You have to solve both the equations and give the answer.
$I$: $\frac{5}{7} - \frac{5}{21} = \frac{\sqrt{x}}{42}$
$II$: $\frac{\sqrt{y}}{4} + \frac{\sqrt{y}}{16} = \frac{250}{\sqrt{y}}$

The largest among the numbers $\sqrt{7}-\sqrt{5}$,$\sqrt{5}-\sqrt{3}$,$\sqrt{9}-\sqrt{7}$,and $\sqrt{11}-\sqrt{9}$ is:

$\left[\frac{3 \sqrt{2}}{\sqrt{6}-\sqrt{3}}-\frac{4 \sqrt{3}}{\sqrt{6}-\sqrt{2}}-\frac{6}{\sqrt{8}-\sqrt{12}}\right] = ?$