Step-by-step explanation:
Given that,
Fencing to be done, P = 400 m
Area of the rectangular garden,

Let l is the length and b is the breadth of the garden. The area of the rectangle is given by :

............(1)
The perimeter of the garden is given by :


...............(2)
On solving equation (1) and (2), we get the value of l and b are as follows :
l = 90 m and b = 110 m
or
b = 90 m and l = 110 m
So, the dimension of the garden is 90 m by 110 m. Hence, this is the required solution.