The side is 8 feet = 8*12 inches = 96 inches
Plants are needed if they are to be spaced 8 inches apart around the outside of the bed
96/8 = 12 ... so we need 12 plants on each side, please note it is including the corners.
If we not incluse corner, the flowers will be 10 each side.
Means total flower : 10 * 4 (each side) + 4(corner)
The total needed is 44 plants. : Answer
Hope that will help :)