Answer:
(-7, 6).
Step-by-step explanation:
All sides are equal since it is a square.
The length of the side joining the first 2 points is |-7 - 6| = 13 units and it is horizontal.
The adjacent side is vertical and also has length 13 and moves up from the last line.
So the missing coordinate has a y coordinate of 6 and an x coordinate of -7.
