y=4.5x+2000 using elimination

I should think at least one additional linear equation would be required to use the elimination method. If you had 8x - y = 100, you could add the two equations together to get 8x = 4.5x +2100. Subtract 4.5x from both sides to get 3.5x = 2100, then divide both sides by 3.5 to get x = 600.

Then insert x = 600 back into the original equation, y = 4.5(600) + 2000 which results in y = 4700.

Or I could be totally off base with what you are asking... apologies if I wasn't of assistance.