All real numbers can be expressed in set builder notation with the following representation:
{ x | x ∈ ℝ }
In this notation, the curly braces indicate a set, and the vertical bar ‘|’ means ‘such that’. Here, ‘x’ represents the elements of the set, and the notation ‘x ∈ ℝ’ means ‘x is an element of the set of real numbers’. This succinctly conveys that the set includes every real number without having to list them all.