x and y chart
sketch graph of y=x-3
plug in any value x and you will get a y value; plot the point (it's wise to pick a point close to x=0)
do this again and just connect both points and you will get the graph.
let's try x = 0
y = 0 - 3
y = -3
so we have one point (0, -3)
let's try another value for x = 1
y = 1 - 3
y = -2
we have the second point (1, -2)
plot these points on a graph and draw a line passing through these points.