Ok, so to solve this problem, you need to find the slope of the line. You know this is what you need to find because units for slope is the y-axis units (dollars) divided by the x-axis units (hours), and your answer must be in dollars per hour based on the question. To find your slope, you use the formula (y2-y1)/(x2-x1). Basically, pick any two points on the graph. I will use (2,20) and (4,40). Now, find the change in x (4 - 2, or 2) and the change in y (40 - 20, or 20) and divide the change in y by the change in x (20/2) to get your answer.
