From the present picture, we can determine two easy point to work with: P1, at (0, 1), and P2 at (2, -3).
To determine the "rise" and "run" lines, we draw a horizontal line which represents the difference of the value in X from P1 to P2, and another vertical line which represents the difference of the value in Y from P1 to P2, as follows:
Now, we will use the following formula to determine the slope of the line:
From the solution developed above, we are able to determine the slope of the line as -2.