How do you solve the following problems? I get confused, can anyone help? Thanks.

(7a^5-a^3)-(a^5-5a^3-1)
(5x-3)(x^3-5x+2)
(4w+5z)^2

1. (7a^5-a^3) - (a^5-5a^3-1)

Remove the parenthesis:
7a^5-a^3 - a^5+5a^3+1
Combine like-terms:
6a^5 + 4a^3 + 1