Respuesta :

Since it is the midpoint we can say:
12x  - 1 = 8x +11
All we have do to is get all the x's alone on one side

12x - 1 = 8x + 11
12x = 8x + 12    (add both sides by 1)
4x = 12   (subtract both sides by 8x)
x = 3       (divide both sides to get what x is)