The 4 angles together will equal 360 degrees. Angle y is the same as the opposite angle of 124 degrees. So we have 2 angles that are 124 degrees. Let's subtract them from 360.
=360 - 2(124)
=360 - 248
=112 degrees for both z and x together
112 is the value of the other two angles (angles z and x), which are also opposite angles. Opposite angles are the same. So we have to divide the 112 degrees equally.
112/2 = 56 degrees for angle and angle x
So angle z = 56 degrees
Hope this helps! :)