Step-by-step explanation:
step 1. ABCD is an isosceles trapezoid because AD and BC are parallel, AB and CD are congruent
step 2. x = 56° (definition of an isosceles trapezoid)
step 3. x + y + z + 56 = 360 (definition of a quadrilateral)
step 4. y = z (definition of an isosceles trapezoid)
step 5. 56 + 2y + 56 = 360
step 6. 2y = 248
step 7. y = 124°, z = 124°.
