Answer:
x = 4
Step-by-step explanation:
We assume that the given expessions represent the measures of the alternate interior angles, so are equal.
... (4x + 12)° = 7x°
... 12 = 3x . . . . . . . divide by degrees, subtract 4x
... 4 = x . . . . . . . . . divide by 3
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Then the angles are 7x° = 28° = (4x+12)°.