Angle AOC and angle BOD are vertical angles. If m∠AOC = (4x + 40)° and m∠BOD = 120°, which equation could be used to solve for x?

The equation that could be used to solve for x is:

m∠AOC = m∠BOD

Since angle AOC and angle BOD are vertical angles, they are congruent. Thus, we have:

(4x + 40)° = 120°