Answer:
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According to the Angles of Intersecting Chords Theorem, the angle between two chords is half the sum of the intercepted arc measures :
- m∠AEC = m∠DEB = (mAC + mDB)/2
Substitute and solve for x:
- 4x = (120 + 2x)/2
- 4x = 60 + x
- 3x = 60
- x = 20