Question

insert two rational number between 3/8 and 7/12

Answer 1

One way to work this is by getting a common denominator :
$\frac{3}{8}=\frac{9}{24}$

$\frac{7}{12}=\frac{14}{24}$

Since the denominator is same, the numbers $\frac{10}{24},~\frac{11}{24},~\frac{12}{24},~\frac{13}{24}~$ lie between the given two numbers.

You may pick any two of them.