Two things to remember:
a. the slope is the rise/run
b. if it is goin from up to down as you look from left to right of the graph then it is a negative slope
So this one is going up three, over 1
so
3/1 which is the same thing as just 3
since the slope is going down from left to right
it is -3
The slope is -3
Hope this helps :)