Geometry

 

   In triangle ABC, the angles \angle A, \angle B, \angle C form an arithmetic sequence.     

   If \angle A + \angle B = 21^\circ, then what is \angle C, in degrees?     

 

   A + B + C  =  180^o     

   A + B         =    21^o     

                C  =  159^o     probably a typo in the problem     

   _.