I'd start by finding the x and y intercepts. If x = 0, then y = 18/4 so your coordinate would be (0, 18/4). When y = 0, then x = 18/5 so your coordinate would be (18/5, 0). Now, if you solve it for y and pick a value for x, like 1 for example, you could find you y very easily.
. Choosing x = 1, you would get y = 5/4 + 18/4 and y = 23/4. So your 3 coordinates could be (0, 18/4), (18/5, 0), and (1, 23/4)