This scene is balanced becuase the couple is placed in the center and there are people placed on either side of them. The background is also symmetric. This all makes it balanced.
This scene is unbalanced because all of the focal points are pulled off to the left side and there is nothing on the right side to balance them out.
This scene is balanced through a triangular design. There are 3 characters at the "points" of the imaginary triangle. The triangle the scene balanced out, and symmetric because there is nothing that is out of the triangle. Everything falls into it's pattern.