A(0,2) and B(6,5) are two points on the straight line ABCD. If AB=BC=CD find the coordinates of the point D

If AB=BC=CD then the difference between each of the points is the same. If we look at the difference between A and B we can see that B is 6 further to the right, and 3 further up. So if we then add (6,3) to B we can get the coordinates of C which would be C(12,8). By doing the same thing again, we can find D with (12,8) + (6,3) so D has the coordinates (18,11).