Estimate the value of $\sqrt{624} \times \sqrt{63} + \sqrt{398} \div \sqrt{17} = ?$

The sum of two numbers is $100$ and their difference is $37$. The difference of their squares is

$A$ fraction is greater than its reciprocal by $\frac{9}{20}$. What is the fraction?

The numerator and denominator of a fraction are in the ratio of $2:3$. If $6$ is subtracted from the numerator,the result is a fraction that has a value $\frac{2}{3}$ of the original fraction. The numerator of the original fraction is

$(\sqrt{2209}-12) \times 5 = ?$

If the sum of two numbers is $33$ and their difference is $15,$ the smaller number is