Answer
$\left\{x| x \lt 3\right\}$
Refer to the image below for the graph.
Work Step by Step
A parenthesis on the right means that $3$ is not included in the set.
Therefore, the set-builder form of the given interval is:
$\left\{x| x \lt 3\right\}$
To graph the interval, plot a hollow dot (or a hole) at $x=3$, and then shade the region to the left of $3$.
(refer to the attached image in the answer part for the graph).
