Solution:
The area of both rectangular gardens is

The area of a triangle is calculated using the formula below

The area of garden B can be represented below as

To figure out the garden design that requires less fencing, we will have to calculate the perimeter of both gardens below using the formula below
The perimeter of GARDEN A will be

The Perimeter of GARDEN B will be

Hence,
Garden A will require less fencing because it has the less perimeter