A rectangle has two pairs of congruent sides, but not 4 congruent sides.
Hello!

In an isosceles trapezoid, both angles on each side of the base are congruent.
∠z ≅ 75°
∠y ≅ ∠x
Because of this, we can get the angle measure for z easily:
m∠z = 75°
Expanding the right side:-
5x - 4 = 5x - 15 + 11
5x - 4 = 5x - 4
left side = right side so there are infinitely many solutions