As given, the number of tiles are = 125
The patio must have area = 80 square feet
Part A.
Assuming the dimensions have to be in exact feet then ,the possible arrangements will be-
As the patio is square, the area is found as = length x length


or

Part B:
For
125-81 = 44 tiles are not used
For
125-100=25 tiles are not used
For
125-121 = 4 tiles are not used.