Missing Angle is 39. 51 degrees + 51 degrees is 102, in order to complete that answer it must all equal to 180. So 180-102 is 78 then since there is two open spots, one above the x and one where the x is, you will divide the 78 by 2 and get 39. 39+39 is 78 51+51 is 102. 102+78 is 180.
