To add and subtract polynomials, combine only like terms. When doing it vertically, stack polynomials and line up the same bases and exponents. Once this is done, simply add and subtract the coefficients.
10x^2 + 12xy + 4x
+ 12x^2 -22xy + 8x
_________________
22x^2 -10xy + 12x
Here we added 10 + 12 = 22, 12 + -22 = -10 and 4 + 8 = 12.
= π Switch the sides to make it easier to read