Answer:
2
Explanation:
You can find the constant rate of change as a slope in a linear graph. We can put the number of the rectangle in the y-axis and which step at x-axis. We can get these three coordinate from the question : (1,1) (2,3) (3,5)
As you can see, the number of rectangle increase by two every step. We can find the slope using the formula just to be sure. Let's say we pick (1,1) as first coordinate and (2,3) as the second coordinate.
m= (y2- y1)/(x2-x1)
m= (3-1)/(2-1)
m= 2/1
m=2
The constant rate of change is 2.