From figure: ∠Y = 120° [Vertical opposite angles]
∠3 + ∠Y = 180° [Linear pair angles theorem]
∠3 = 180 – 120
∠3 = 60°
Line l is parallel to line m,
∠1 = ∠3 [ Corresponding angles]
∠1 = 60°
Also, line m is parallel to line n,
∠2 = ∠Y [Alternate interior angles are equal]
∠2 = 120°
Answer: ∠1 = 60°, ∠2 = 120° and ∠3 = 60°.