Sorry but I can't understand your language
(3+3+3+3=12) (3x4=12)
(-3) +(-3)+ (-3)+ (-3)= (-12) (-3x4=-12)
If M <span>is the midpoint of AB then AB = 2AM
8x - 6 = 2(3x + 3)
8x - 6 = 6x + 6
8x - 6x = 6 + 6
2x = 12
x = 12/2
x = 6
AM = 3x + 3 = 3*6 + 3 = 18 + 3 = 21 units
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