We can first get the side length for the square because a square has 4 sides of equal length.
4 x side length = 36 ft
side length = 9 ft
If you increase the length by 3 ft and decrease the width by 5 ft, we will get a 12 ft by 4 ft rectangle as a result.
length = 9 + 3 = 12 ft
width = 9 - 5 = 4 ft
The area of the rectangle is...
12 x 4 = 48 ft²
answer: 48 ft²