Add: (x^3+x^2) + (2x^3-5x^2)

We can ad like terms basically

x^2 can be added to 2x^2 but not 3 or 2x^4

so we have

(x^3+x^2) + (2x^3-5x^2)

using associative and commutative property

remove the parenthaseese

x^3+x^2+2x^3-5x^2

and move them around so group the like terms

1x^3+2x^3+1x^2-5x^2

add

3x^3-4x^2

tada

X^3+x^2+2x^3-5x^2

Solution: 3x^3-4x^2