Answer:
y= -2x + 80
Explanation:
First, you need to find the slope, which can be done by subtracting the change in y over the change in x. The easiest points to pick are (30,20) and (40,0). Do 20-0 which is -20, then divide that by 40-30, and you get -2. Then to find the y intercept, pick a point (like 40,0). Then do 0 = -2(40) + b, and solving for b you get 80.