Find the values of each angle in the quadrilateral

a) Angles 1 and 2 of this isosceles trapezoid are equal and supplementary to angles D and 3, which are also equal.
  ∠1 = ∠2 = 180° -55° = 125°
  ∠3 = ∠D = 55°

b) Top and bottom angles are equal.
  (4x+15) = (5x-13)
  28 = x . . . . . add 13-4x
The value of x is 28.

“exterior angles of triangles. an exterior (or external) angle is the angle between one side of a triangle and the extension of an adjacent side. try this drag the orange dots on any vertex to reshape the triangle.” look to get to the answer i explained what it means and other things i hope it you .