What is the value of $4^{3}-3^{2}+6^{2}-5^{2}+8^{2}-7^{2} ?$

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?

$\left(\frac{24}{9}\right)^{2} \times \frac{399}{39} \div \frac{41}{899} = ?$

$(0 . \overline{09} \times 7 . \overline{3})$ is equal to

$7 \frac{1}{2}-\left[2 \frac{1}{4} \div\left\{1 \frac{1}{4}-x\left(1 \frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\right\}\right]=3$. Find the value of $x$.

What will come in place of the question mark (?) in the following expression?
$(4444 \div 40) + (645 \div 25) + (3991 \div 26) = (?)$