Depends on the shape we are talking here. I believe you are taking about a square, so:
The equation for area for a square is: s^2, s representing the length of 1 of the squares sides (a square is even all the way around, so 1 side is the same as all)
8^2=64, so I can assume this is a square by this. Knowing it's a square, and that one of the sides is equal to 8, and the other 3 sides are the same length, I can do 8*4, which equals 24.
The perimeter is 24