y = 2.5x is the same as y = 2.5x + 0
0 Will be your beginning point (where you start)
2.5 will be your slope
You would put a point at (0,0), or the origin
Then you would use the
strategy to find out how steep the line would be. Rise = ↑, Run = →. You would rise (go up ↑) first, then you would run (go right →). The strategy is using the number next to x for rise, and you would use 1 for run.

In this case, you would rise up 2.5 ↑, and run right 1 →.
You will repeat the
strategy until you see a clear line on your graph.