The rate of change is -5/4
I find it best to use the Slope formula
M= y2-y1/x2-x1
So we to use need any 2 points on the graph (I used the first 2)
•(0,200) and (80,100)
Now we set up the problem 100-200/80-0
Then you’ll subtract and should get
-100/80
Now you’ll simplify and once you’re done simplifying your answer should be -5/4.
Here is my work. Hope this Helps!