Any of them really cause they don't set there and count them out one by one there is always a different ammouth in each bag
Step-by-step explanation:
The way that I would do it, would be to use the point distance formula to find the length of each side.
Distance formula: 
After you use this formula to find the length of all sides of the polygon, you would need to use the appropriate area formula to find the area of the polygon.
Area of Triangle: A= 1/2 base times height
Area of Rectangle: A= length times width
Area of Square: A= s^2 where s is the length of the side
Area of Parallelogram: A= base times height
Area of Trapezoid: A= 1/2 times height (base 1 + base 2) where base 1 and base 2 are the parallel sides
Area of Kite or Rhombus: A= 1/2 (diagonal 1 times diagonal 2)
Area of Regular Polygons: A= 1/2 (apothem times perimeter)
Just divide 84 / 7 and will be 12
A square is the same length on each side so each side would be 9
9+9+9+9= 36ft (perimeter)
Again each side if 9 feet to find the area u just multiply the length and width here the length and width are the same (9)
9•9= 81 (area)