The the number of feet needed for the fence of the rectangular garden = its perimeter = 252 ft.
Perimeter = 2(length + width).
The number of feet needed for the fence around the rectangular garden = perimeter of teh rectangular garden.
Given the following:
Plug the values into Perimeter = 2(length + width):
Perimeter of the rectangular garden = 2(42 + 84)
Perimeter of the rectangular garden = 252 ft
Therefore, the the number of feet needed for the fence of the rectangular garden = its perimeter = 252 ft.
Learn more about perimeter of rectangle on:
https://brainly.com/question/24571594