What will come in the place of question mark $(?)$ in the following expression?
$561 \div 35.05 \times 19.99 = ?$

When $52416$ is divided by $312,$ the quotient is $168.$ What will be the quotient when $52.416$ is divided by $0.0168?$

If $x^{2}+y^{2}+z^{2}+2=2(y-x)$,then the value of $x^{3}+y^{3}+z^{3}$ is equal to

$3 \div \left[ (8 - 5) \div \left\{ (4 - 2) \div \left( 2 + \frac{8}{13} \right) \right\} \right] = ?$

$16.02 \times 0.001 = ?$

The denominator of a fraction is $3$ more than the numerator. If the numerator as well as the denominator is increased by $4,$ the fraction becomes $\frac{4}{5}$. What was the original fraction?