In tables, graphs and equations, we have x values and corresponding y values. On the graph, we can pick a point on the horizontal axis and draw a vertical line to touch the line on the graph. The y coordinate of the point where the vertical line touches the line on the graph is the corresponding y value. When we divide a y value by its corresponding x value, we would compare the result by dividing another y value by its corresponding x value. If the results are the same, then the value gotten is the constant of proportionality.