It will cost $360 to enclose a square garden.
We need to find the perimeter of the square to know the number of meter needed and multiply it to the unit cost of the fence to get the total cost.
Given:
fence = 7.50 per meter
Area of a square = 144 m²
Area of a square = s²
s = √144m²
s = 12m
Perimeter of a square = 12m x 4 sides = 48 meters.
48 meters x $7.50 = $360