Both angles are vertical angles. According to the Vertical Angles Theorem, vertical angles are congruent. Therefore:
6x°=120° [Vertical Angles Theorem (vertical angles are Congruent)].
6x/6=120/6 [Division P.O.E]
x=20.
Therefore, if x=20, then:
6(20)=120 [Substitution P.O.E.
120=120 [Symmetric P.O.E]
And thus,
x=20
