Answer:
x=20°
Explanation:
This is actually simpler than it seems. Try redrawing (or maybe just imagine) that the only inscribed angle is x with the two lines going to the 40°. If we let 40°=θ, then: x=θ/2
This is actually true for any situation with inscribed angles, so you could use this to find w, y, and z as well.
Anyways x=(40°)/2=20°, so x=20°