This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
AB is a chord of the circle.  Chord AB makes an angle at the center which is twice the angle it makes at a point on the circumference. 

   hence  w = v = x/2

in the quadrilateral,  CGDH,
         angle C = y  (vertical angle)

 sum of angles in the quadrilateral CGDH is

     180 - v + y + 180 - w + z = 360

  hence,         w + v  =    x = y + z

11 3 11
click oon thank you link and select best answer