$\frac{69842 \times 69842 - 30158 \times 30158}{69842 - 30158} = ?$

If $a+b+c=1$ and $ab+bc+ca=\frac{1}{3}$,then $a:b:c$ is

What is the value of $999 \frac{1}{2} + 999 \frac{1}{6} + 999 \frac{1}{12} + 999 \frac{1}{20} + 999 \frac{1}{30}$?

$7^{5} \div 7^{3} \div 7^{2} \times 7^{4} \times \frac{1}{7^{3}} = 7^{?}$

If $a = \sqrt{2} + 1$ and $b = \sqrt{2} - 1,$ then the value of $\frac{1}{a + 1} + \frac{1}{b + 1}$ will be

What value will come in place of the question mark (?) in the following question? (You are not expected to calculate the exact value)
$21 + 39 \times 2.9 + 8.99 = ?$