First, you have to identify which type of relation the points have. From the graph you can tell that it's an exponential growth. The x values change in the same amount every time, in this case by 1.
So if the relation is exponential, if we divide the y coordinates you should get the same result every time.
18 / 6 = 3
54 / 18 = 3
162 / 54 = 3
So the y value increases 3 times. That means that the next value should be 162*3 = 486.
