The slope of a line can be found by dividing the rise over the run between two points. The rise is the difference between the y-values, and the run is the difference between the x-values. For both, the value with the greater x-value comes first as you are seeing how much it has changed from the first value to the the other.
Let's use the first two points to find the slope: (0,9), (2,4)
(2,4) has the greater x-value, so the rise between the points would be -5, as 4 - 9 = -5
