Take two sets of points, and use the formula [tex]y_2-y_1/x_2-x_1[/tex], where y1= the y-coordinate of the first point y2 = the y-coordinate of the second point and x1= the x-coordinate of the first points x2= the x-coordinate of the second point.
If you want a walkthrough of how to use this formula, PM me and I'd be glad to help you as soon as I can :)
