I can't see the figure entirely. To solve for the perimeter you need to know the height!
The answer to the question is d.
I’ll solve number 3.
You need to group the like terms. For example, -4n + 6n = 2n
8=2n
Now, we need to keep n by itself.
2n/2 = n
Whatever you do to one side, you need to do to the other.
8/2 = 4
So, in conclusion, n = 4.
I hope this helps for you to solve the rest!