For the all questions we use the theorem of chords and arcs and get that for the first question:

Now, to find angle D:

Next for arcAC we use that WC and WA are tangent to the circle
O is the center of the circle ( O is not E). Now we recall that the inner angles of a quadrilateral is 360 so

By the definition of arcAC

Finally we use the fact that the value of inscribed angles is half of the value of the central angle, using this we get :
