The measure of ∠XYZ is 40°.
The measure of the central angle is equal to the measure of the minor arc. Since Arc XZ is the minor arc, central angle is equal to 140°.
∠XYZ = 1/2 (major arc - minor arc)
∠XYZ = 1/2 (220 - 140)
∠XYZ = 1/2 (80)
∠XYZ = 40°
I also solved the problem using the right triangles that are formed in the figure. Pls. see attachment