22. AC || BD, ∠AOB — ?

Since AC || BD, the alternate interior angles are equal. Let $$\angle CAO = 80^{\circ}$$ and $$\angle DBO = 40^{\circ}$$. Then, $$\angle AOB = 180 - (80 + 40) = 180 - 120 = 60^{\circ}$$. **Answer: 60°**