The angle that measures 84° and the angle that measures 4x are vertical angles. This means that their angle measures are congruent. Thus, the value of x is 21°
84° = 4x 84° / 4 = x 21° = x
Angle M and the angle that measures 84° are supplementary angles. This means that the sum of their measure equals 180°. Thus, angle M measures 96°.