XOY is a straight line (180°).

From the figure, the angles on the straight line relate to ∠YOZ and ∠WOX.
∠YOZ : ∠WOX = 3 : 10, total = 13 parts.
A right angle of 90° is also present. ∠YOZ + ∠WOX = 130°.
1 unit = 130° ÷ 13 = 10°.
∠YOZ = 3 × 10° = 30°.

Final Answer: 30