To find the midpoint, the formula would be:
x1+x2 y1+y2
-------- , --------
2 2
In this case, we do not know x2 or y2 (these are the 2nd set of coordinate points), but we know the coordinate of the midpoint. We can use these to make an equation
3+x
------ = 5
2
First, multiply each side by 2 to get rid of the fraction
3+x=10
Subtract 3 from each side
x=7
5+y
------ = -11
2
Multiply each side by 2
5+y=-22
Subtract 5 from each side
y=-27
The coordinate would be (7,-27)
To check your work, plug the coordinates for point U,V, and the midpoint into the formula.
3+7/2=5
10/2=5
5=5
5+-27/2=-11
-22/2=-11
-11=-11
The other endpoint is equal to (7,-27)