How much is #(4x^2 - 19x + 15) + (-18x^2 + 15x + 16)#?
Note : I removed the word "greater" from the question (which is something I normally do, since "How much greater is something + something-else ?" doesn't make any sense).
If you meant "How much greater is something than something-else ?", please re-post in a meaningful form.