Answer: x = 28
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Step-by-step explanation:
The angles COE, EOF, and FOB combine to form angle COB
angle COB = (angleCOE)+(angleEOF)+(angleFOB)
angle COB = (3x)+(x)+(x+12)
angle COB = 5x+12
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Angles AOD and COB are vertical angles, so they are congruent
angle COB = angle AOD
5x+12 = 152
5x = 152-12
5x = 140
x = 140/5
x = 28