On a graph, when a line is going up or down, that is y. When it is going horizontally, that is x. So they can be used as points. For example, if the coordinates were 3, 4, (x, y), then you would first go across 3 on the graph and then go up 4. There you would plot your point. It can also be used in equations. For example, if the equation was.. 2x + 3y, and the coordinates were 1, 2, (x, y), then x would be 1 and y would be 2. In order to solve, you would plug in x and y. Hope this helps. If you could give me the brainiest answer that would be greatly appreciated.