Question

The numerical value of $b$ is $x$ times the actual volume occupied by one mole of gas molecule, then $x$ is

Answer 1

The numerical value of $b$ is $x$ times the actual volume occupied by one mole of gas molecule, then $x$ is 4.
The effective volume, also called co-volume or excluded volume, of the molecules in motion has been calculated to be four times the actual volume of the molecules at rest.
$b=4V_m$