Find X if m < GHU = 60º
m < GHI = 12x +1,
and m < UHI = -11+8x.
Assuming Point I is in the interior of angle GHU....because there isn't a diagram or any confirmation.
The angle addition postulate states that if Point D is in the interior of Angle ABC, then Angle ABD + Angle CBD = Angle ABC.
Applying this to your problem, gives: (12x+1) + (-11+8x) = 60
Combine like terms: 20x-10=60
Solve for x: 20x=70
x=7/2, or 3.5
You can check your work by plugging x in for the angles, and seeing if sum of the angles equals 60 or not.
43+17=60, meaning that its correct.