Objective Function... Need help~

I have read my textbook N times... but I still have no idea how to draw the Objective Function graph...

For example:
z=125x+200y, where
x (less than) 450;
y (less than) 200;
600x + 900y (less than) 360000

I can graph the first two, for sure...
but what about the last one? How do I graph it?

As I know, 600x + 900y means the slope is 2/3.
But what about the 360000?

Please help... lots of questions still waiting for me...!
Thank you.