What is the value of $(2.3+1.7)^{2}-(2.3-1.7)^{2} ?$

If $\frac{x}{y} = \frac{4}{5}$,then the value of $\left(\frac{4}{7} + \frac{2y - x}{2y + x}\right)$ is

Determine the value of $x$. If $x = \frac{(943 + 864)^{2} - (943 - 864)^{2}}{(1886 \times 1728)}$

What approximate value will come in place of the question mark $(?)$ in the given equation? (You are not expected to calculate the exact value)
$2775 \times \frac{160}{\sqrt{?}} = 5550$

If $a+b+c=6, a^{2}+b^{2}+c^{2}=14$ and $a^{3}+b^{3}+c^{3}=36,$ then the value of $abc$ is

$989.001 + 1.00982 \times 76.792 = ?$