Answer
See below.
Work Step by Step
The three methods of representing sets are:
1) by Word Description. E.g. S is the set of positive integers that are less than $4$.
2) by the Roster Method. E.g. $S=\{1,2,3\}$.
3) by the Set-Builder Notation. E.g. $S=\{x|\text{ x is an integer less than $4$}\}$
