Which pair of terms is a pair of like terms?

In the term $-6a^3$, which number is the coefficient and which is the exponent?

Simplify $(4x^3+3x-5)+(-x^3+7-2x)$.

Simplify $(4x^2+6x)+(-x^2+2x)$ and factor the result by pulling out the greatest common factor.

Simplify and evaluate the polynomial $(2x^2-3x+5)+(-x^2+4x-2)$ at $x=2$.