$2438.79 - 1233.99 + 399.99 = ? + 989.99$

$(\sqrt{4489}-\sqrt{2601})=(?)^{2}$

If $x[-2\{-4(-a)\}]+5[-2\{-2(-a)\}]=4 a,$ then $x=$

$A$ two-digit number has $3$ as its unit's digit,and the sum of its digits is $\frac{1}{7}$ of the number itself. The number is:

$\frac{6}{5}$ of $\frac{3}{4}$ of $\frac{1}{2}$ of $? = 3600$

$A$ fraction becomes $4$ when $1$ is added to both the numerator and denominator; and it becomes $7$ when $1$ is subtracted from both the numerator and denominator. The numerator of the given fraction is