Let the ABCD be isosceles trapezoid (AB=CD), AC is equal to AD and angle B is equal to 128 degrees. Let's find the value of angle CAD.
In case, that you have already solved this problem, have found required angle, then you might still be wondering "where is a pig in a poke ?"... Just ask yourself: what is the value of BAD angle?
Tomorrow you will get full explanation of this problem and different ways to avoid this absurdity.
Have a nice day/evening/morning!