Answer:
The other two co-ordinates are (-3, 5) and (-8, 5).
Step-by-step explanation:
Consider the rectangle ABCD.
A = upper-left coordinates = (-8, 8)
B = upper-right coordinates = (-3, 8)
C = lower-left coordinates
D = lower-right coordinates
Let the side AB form the length of the rectangle.
Compute the distance between the points A and B as follows:


The length of the rectangle ABCD is 5 units.
The are of ABCD is given as 15 square units.
Compute the breadth of the rectangle as follows:

So, the breadth of the rectangle is 3 units.
Then from point B, 3 units below would be (-3, 5).
And from point A, 3 units below would be (-8, 5).
The rectangle on the coordinate plane is attached below.