Finding the Number of New Members

Consider the following scenario involving integers:

A school club has a total of 36 members. During one event, the number of new members was equal to the number of members who left the club. After the event, the total number of members in the club became 40. If we represent the number of new members who joined the club as $x$, and the number of members who left as also $x$, which integer represents the value of $x$?