Algebra Math Help

However, I am not sure about a few of the problems.

If anyone could just check if these answers are correct, I would greatly appreciate it!

(IF they are wrong, could you explain how I could get the correct answer?)

Here they are:
6) Simplify: (3n – 4n^2 + 9) + (7n^2 – 5n – 6)

I got: 3n^2 – 2n +3
—-
Simplify: (4p^2 + 5p – 2) – (p – 3p^2 – 7)

I got: p^2 + 4p + 5

—-
5) Find the product, and then find the degree of that product:
-3x^2(4x^3 – 2x^2 + 5)

I got: -12x^5 + 6x^4 – 15x^2 and the degree is a quintic.

( The ^ symbol means to the power of )

Those are it,

THANKS in advanced!
OOPS!

#8 is actually (4p^2 + 5p – 2) – (x + 3p^2 – 7)

Sorry!