Which fraction among $\frac{3}{7}, \frac{5}{11}$,and $\frac{6}{13}$ is the largest?

$A$ and $B$ are positive integers. If $A + B + AB = 65$,then what is the difference between $A$ and $B$ (given $A, B \leq 15$)?

$(\sqrt{9})^{3} \times (\sqrt{81})^{5} \div 27^{2} = 3^{?}$

$A$ 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

$63 + 371 \div 7 = ?$

If $a$ and $b$ are odd numbers,then which of the following is even?