The rate of change, also known as the slope of a line, is a measure of how fast the line changes in the vertical direction compared to the horizontal direction. Typically, the vertical axis is the y-axis, and the horizontal axis is the x-axis.
The rate of change can be calculated by taking the difference between the y coordinates of two points, and dividing it by the difference of the x coordinates of the same two points. For example, for the points (2,80) and (4,160), the slope is equal to 160 minus 80, divided by 4 minus 2. This is equal to 80 divided by 2, or 40.