$\frac{180 \times 15 - 12 \times 20}{140 \times 8 + 2 \times 55} = ?$

What will be the remainder when $252^{126} + 244^{152}$ is divided by $10$?

Which one of the following is the smallest fraction?
$\frac{6}{11}, \frac{13}{17}, \frac{19}{27}, \frac{21}{23}, \frac{5}{7}$

If $a = 7 - 4 \sqrt{3}$,the value of $a^{\frac{1}{2}} + a^{-\frac{1}{2}}$ is

If $x = \frac{4 \sqrt{ab}}{\sqrt{a} + \sqrt{b}}$,then what is the value of $\frac{x + 2 \sqrt{a}}{x - 2 \sqrt{a}} + \frac{x + 2 \sqrt{b}}{x - 2 \sqrt{b}}$ (when $a \neq b$)?

If $x = (0.25)^{\frac{1}{2}}, y = (0.5)^{2}, z = (0.216)^{\frac{1}{3}},$ then