In the following figure, find the unknown angles a and b, if l||m.

Here, l || m

∠c = 110° (Corresponding angles)

∠c + ∠a = 180° (Linear pair)

⇒ 110° + ∠a = 180°

⇒ ∠a = 180° – 110° = 70°

Now ∠b = 40° + ∠a (Exterior angle of a triangle)

⇒ ∠b = 40° + 70° = 110°

Hence, the values of unknown angles are a = 70° and b = 110°