Given the Perimeter of the Lot is 436 ft, and an inner building whose base measures 122ft by 60ft. The key in the problem is that the easement is uniform.
Let X be the measure of easement. See attached
You will derive the equation where if you add X on the length of the inner rectangle length and width, you have below equation
P = 2L + 2W
P = 2*(122+2X) + 2*(60+2x)
436 = 244+4x + 120+4x
Rearranging the equation by shifting all constant on one side.
8x = 436-244-120
8x = 72
x=9 ft
Answer is 9ft easement for with respect to the base of the inner building.