In the form #y = mx+b#, #b# is the #y#-intercept. That means your line should cross the #y#-axis at #y=-200#.
The slope, #m#, is 1. That means for every #x#-unit across, you go one #y#-unit up.
Depending on how big you graph is, it might take ages to plot every point. If you don't want to do that, find the #x#-value on your graph that is farthest to the right. Find its #y#-value (The #x#-value minus 200) and plot the point. Then, do the same for the leftmost point in the graph. These two points need to be really, really accurate for this to work. Gat a ruler and draw a line (Remember, be accurate!) connecting the two points. Ta da! you have a line. Just to check if it's right, check if the line crosses the #y#-axis at #y= -200#.
graph{x-200 [-382.7, 484, -280.3, 153.4]}
