Slope is defined simply as delta y over delta x or the change in y over the change of x. We need to decided what points is going to be the start or the end. Typically, the point farther to the right of the graph is considered the end point.
Start: (1, 7)
End: (10, 1)
[tex]m = \frac{1 - 7}{10 - 1} \\\\\\m = \frac{-6}{9} \\\\\\m = \frac{-2}{3}[/tex]
