k is the slope of the line formed by connecting the points.
Use slope formula:
[tex] \frac{y_2 - y_1}{x_2 - x_1} [/tex]
where the 2 points are the end points of the line (First and last going Left to right)
[tex](x_1,y_1) = (2,7) \\ (x_2,y_2) = (8,28)[/tex]
Substitute into slope formula
[tex]k= \frac{28-7}{8-2} = \frac{21}{6} = \frac{7}{2} [/tex]
You can check if this is correct by going back to graph and going "up 7" and "over 2" to get from one point to the next.
