Answer:
Equation: 2x + x = 180
x = 60
∠GFH = 120
∠CBD = 60
Step by step:
Use 2x + x = 180 because the angles are on a straight line meaning they have a sum of 180:
2x + x = 180
3x = 180
3x/3 = 180/3
x = 60
Now just substitute:
∠CBD = x = 60
∠GFH = 2x = 120