You can use the slope formula to figure this out, or you can just use common sense.
m(slope)=y2 - y1 / x2 - x1
Two points of the line are (3,1) (5,-3)
(-3 - 1) / (5-3) = -4 / 2 = - 2
Or you can just do rise over run (slope).
The line goes right 1 (run) and down 2 (rise)
Down 2 = -2
-2/1, or -2
-2 is your answer.