Answer
$x \lt 4$
Please see image
Work Step by Step
$ 15-3x\gt 3\qquad$ ...add $-15$ to each side of the inequality.
$ 15-15-3x\gt 3-15\qquad$ ...simplify.
$-3x\gt-12\qquad$ ...divide with $-3$.
...dividing with a negative inverts the inequality sign.
$x \lt 4$
The solutions of the given inequality are all real numbers smaller than $4$.
Smaller numbers are to the left of $4$.
Use an open dot in the graph to indicate $4$ is not a solution.
