
Tracy D. answered 10/06/20
Experienced SAT Math Test Prep Tutor
The embedded angle is "inside" the whole angle (draw a picture for yourself, it will help a LOT). So, if you know the whole angle, and one side of the inside, the the other side is just the whole - one side to get the other side.
Angle NOQ - Angle NOP = Angle POQ
123°-37°=86°