please explain how to do this one it says to simplify by adding like terms
2x^2 y+3yx^2+x^2 y-x^2 y-4x^2 y^2

I think my maths is OK for this. Other posters may knock me back at will but if you extract each term of the statement it looks easier:

2x²y + 3yx² + x²y - x²y - 4x²y²

1) 2x²y

2) 3yx²

3) x²y

4) - x²y

5) - 4x²y²

For a start terms 3 and 4 cancel each other...

and terms 1 + 2 can be added, just because they are written slightly differently x²y and yx² doesn't matter

So you should end up with

5x²y - 4x²y²