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M = (6, 3)
A = (7,4)
B = (x,y)
Formula
Mx = (x1 + x2) / 2
My = (y1 + y2) / 2
Solve for x2 and y2
x2 = 2Mx - x1
y2 = 2My - y1
Substitution
x2 = 2(6) - 7
y2 = 2(3) - 4
Simplification
x2 = 12 - 7
y2 = 6 - 4
Result
x2 = 5
y2 = 2
Conclusion
The coordinates of B are (5,2)