Answer
$(-\infty,5]$
See the figure below.
Work Step by Step
Since the right boundary of the given inequality involves "less than or equal", then the interval notion will have a bracket on the right and a paranthesis on the left.
Hence, the given inequality can be written as $(-\infty,5]$
To graph, plot a solid dot at $x=5$, then shade the region from 5 till its left.
See the figure below.
