The rate of change is equal to the slope of a line. Given any 2 points on a line and you can calculate the slope (rate of change) of that line. The formula for rate of change is given by Δy/Δx which equals (y2-y1)/(x2-x1). Therefore, using the points given in the question and simply input them into our formula, we get ((4)-(3))/((-2)-(0)) = -1/2