Angle ∠5 and ∠6 are internal corners. Since their sum is 180, straight lines A and B are parallel.
By condition, the angle ∠4 = 120, then the angle ∠1 is also equal to 120, since these are the vertical angles at the intersection of lines A and C.
Angle 2 is equal to angle ∠1 as criss-crossing angles at the intersection of parallel lines A and B secant C. Angle ∠2 = 120.
Angle ∠3 and angle ∠2 are vertical angles, then angle ∠3 = 120.
Answer: Angles 1, 2, 3 are equal to 120.
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