I graphed it. This is to avoid confusion and to understand the problem clearly.
Given:
1st corner : 2,3
2nd corner : -1,3
3rd corner : -1,-1
4th corner : ? ⇒ 2,-1
Length is 4 ; Width is 3
Perimeter of a rectangle = 2(L + W)
P = 2(4 + 3)
P = 2(7)
P = 14
The perimeter of the garden is 14.