Answer:
Step-by-step explanation:
I can't explain this any other way than to give you the answer.
On the right hand side, 18 and - 1 are like terms.
They are both integers and they are both without x's attached to them. That's what like means. The terms don't have letters attached to them,, but if they do, the letters are exactly the same.
4x + 5x = 9x
4x^2 + y^2 does not combine.
