The difference between one-fourth of a number and one-seventh of the same number is $24$. What is the number?

$\left[(72)^{2} \div 36+(?)^{2}\right] \div 5=45$

How many numbers are there between $1$ and $200$ which are divisible by $3$ but not by $7$?

$\left[ {8\left\{ {\left( {\frac{{21 \times \sqrt {\frac{9}{{441}}} }}{5} \text{ of } 60\% - \frac{1}{5}} \right) \times 625 + 7} \right\} \div 4} \right] = ?$

The expression $\frac{8.25 \times 8.25 + 6.75 \times 6.75 - 2 \times 8.25 \times 6.75}{8.25 \times 8.25 - 6.75 \times 6.75}$ when simplified equals:

The sum of squares of two numbers is $90$ and the square of their difference is $46$. The product of the two numbers is