Compare x to x and y to y.
In this case, the first x is 5 and the second x is 3.
[Remember the point format is (x, y).]
5 to 3 on the number line is -2.
Then the first y is 9 and the second is also 9.
9 to 9 on the number line is 0.
Also, recall that the slope is the change in y over the change in x so the slope is:
0/-2
Hope this helps. (: