#### Answer

Refer to the graph below.

#### Work Step by Step

RECALL:
The graph of the equation $f(x)=k$ is a horizontal line whose y-intercept is $(0, k)$.
Every point on the line has a y-coordinate of $k$.
Thus, the graph of the equation $f(x)=3$ is a horizontal line and every point on the line has a y-coordinate of $3$.
This means the following points are on the line: $(-3, 3)$ and $(3. 3)$.
Plot the two points above and connect them using a straight line.
(Refer to the graph in the answer part above.)