Please help me solve these 3 problems relating to geometry of a circle.

1) ABCDEF is a hexagon inscribed in a circle. What is x + y + z?

2) In this figure, find the value of angle ABC + angle ADC and figure out if ABCD a cyclic quadrilateral. Therefore, find angle BDC

3a) In this figure, AOB is the diameter. Prove that points OAMP are concylic.

3b) Find two angles equal to angle OPA.

Thanks for any help.