Respuesta :

If M 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