I am not sure, but if you mean how to answer, x2-8x, then, this is how to answer that equation. In the law of Algebra, the constant always comes first before the variable, so it should be that x2 is 2x using the law, so lets answer.
2x-8x=(just think of it like fractions wherein in fractions you copy the same denominator, but here, in this equation, you copy x. Just think that it is 2-8, then copy x)
-6x + 8x= 2, true
Therefore you do this equation like they are integers and copy x.