Answer
$\left\{x| x \le 3.5\right\}$
Refer to the image below for the graph.
Work Step by Step
A bracket on the right means that $3.5$ is included in the set.
Therefore, the set-builder form of the given interval is:
$\left\{x| x \le 3.5\right\}$
To graph the interval, plot a solid dot at $x=3.5$, and then shade the region to the left of $3.5$.
(refer to the attached image in the answer part for the graph).
