$\sqrt{5^{2} \times 14 - 6 \times 7 + (4)^{?}} = 18$

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 number of five digits which is a perfect square is

Find the least number,which,when multiplied with $74088$ will make it a perfect square.

$\sqrt{33124} \times \sqrt{2601} - (83)^{2} = (?)^{2} + (37)^{2}$

If $\sqrt{12} = 3.464$,the value of $\sqrt{\frac{3}{4}} + 2 \sqrt{\frac{4}{3}}$ is