We can calculate the slope of a line (m) by means of the formula:
[tex]m=\frac{y2-y1}{x2-x1}[/tex]
Where (x1,y1) and (x2,y2) are two points of the line.
In this case, we can take the points (2,2) and (6,0) from the table to get:
[tex]m=\frac{0-2}{6-2}=\frac{-2}{4}=-\frac{2}{4}=-\frac{1}{2}[/tex]
Then, the slope of the line equals -1/2
