i forgot how i solved this and i need help understanding the second step done by lorne, thank u!

Given:
[tex](-3x^3+5x^2+4x-7)+(-6x^3+2x-3)[/tex]The second step is writing the terms individually and the addition sign between them, so, we will use the property of the opposite addition
For example, instead of writing: (1 - a), we can write it as 1 + (-a)
So, the expression will be:
[tex](-3x^3)+5x^2+4x+(-7)+(-6x^3)+2x+(-3)[/tex]