If $4x + 5y = 83$ and $\frac{3x}{2y} = \frac{21}{22}$,then $y - x = ?$

What is the value of $\frac{2.75 \times 2.75 \times 2.75 - 2.25 \times 2.25 \times 2.25}{2.75 \times 2.75 + 2.75 \times 2.25 + 2.25 \times 2.25}$?

What will come in the place of the question mark $(?)$ in the following expression?
$\sqrt{15^{2} \times 12 \div 9 - 125 + 21} = ?$

The value of $\frac{2^{1 / 2} \cdot 3^{1 / 3} \cdot 4^{1 / 4}}{10^{-1 / 5} \cdot 5^{3 / 5}} \div \frac{3^{4 / 3} \cdot 5^{-7 / 5}}{4^{-3 / 5} \cdot 6}$ is

The value of $3+\frac{3}{3+\frac{1}{3+\frac{1}{3}}}$ is:

What will come in the place of the question mark $(?)$ in the following equation?
$(21)^{2} - 3717 \div 59 = ? \times 8$