Answer:
The largest rectangular space is 
Step-by-step explanation:
Given a 20m long wire fence, implies that the perimeter of the fence has been given, because Perimeter can be defined as the length of the boundary of a figure (in this case, a rectangle)
So, from the formula: Perimeter = 2 (L + B) = 
We have that L + B = 
The possible values of L and B are:
(L, B) = (9, 1), (8, 2), (7, 3) and (6, 4).
The areas of the rectangle that will be formed using these values are respectively;
,
,
and
, the largest area of which is the last which corresponds to the values (6, 4).
The largest rectangular space that the gardener can enclose is therefore 