If you look at that angle it is part of a triangle. All angles of a triangle equal 180 degrees. The right and top corners are vertical (equal) to the pink(top) green (right). So 58(top)+76 (right)= 134. You subtract 134 from 180 you get 46. X=46
180-[58(top)+76 (right)]=x
if u have any questions lmk