Area of a Triangle: A=B(H)
B means Base
H means Height
Point D on the grid is exactly 5 plots away from Point E
Line DE = 5, Line DE is Also your base
So 5(?Height?) = 15
The Height has to be 3
So the possible point has to lie on that horizontal 3 line... it can almost go anywhere on it.
Try
(4,3)
Or~
(5,3)