Question 50192
the coordinate of point T are given. the midpoint of ST has coordinate (5,-8). find the coordinates of points S. 
You have to know that the coordinates of the midpoint are the average of 
the x-values of the end points and the y-values of the end points.
1. T(0,4)
Let S have coordinates (x,y)
Then (x+0)/2 = 5; x=10
And (y+4)/2 = -8; y=-20
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2. T(10,18)
Let S have coordinates (x,y)
Then (x+10)/2 = 5; x=0
And  (y+18)/2 =-8;  y=-34

Cheers,
Stan H.