you add everything with the same power of x together, for exmple you have 2x^3 and the 3x^3 the x^3 is the same in both so you just add it to get 5x^3, then you do the same thing for everything collect the like terms, those who have x^2 is only -4x^2 that's the only thing left, so you write it down, and proceed to x
