Answer
$m=\dfrac{-3}{2}=-1.5$
Refer to the graph below.
Work Step by Step
The slope of the line can be determined by the equation:
$m=\dfrac{y_2-y_1}{x_2-x_1}$
where $(x_1, y_1)$ and $(x_2, y_2)$ are two given points on the line.
Here, we can substitute in the coordiantes of the points $(2,3)$ and $(4,0)$ to obtain:
$m=\dfrac{0-3}{4-2}=\dfrac{-3}{2}=-1.5$
The graph is in the picture below.