y = (1/3)x + 3
Pick a value for x. Let's say x = 3.
y = (1/3)(3) + 3
y = 1 + 3
y = 4
So now you have a point (3,4).
Pick another value for x. Let's say x = -6.
y = (1/3)(-6) + 3
y = -2 + 3
y = 1.
No you have another point (-6,1).
2 points form a line, so you can just draw a line connecting (-6,1) and (3,4).