Find the angles (∠P, ∠Q, ∠R) of the given triangle if a + b = 120° and a – c = 30°.

Given, 

a + b = 120°  ———— (i)

and a – c = 30°———— (ii)

In ∆ PQR, ∠P + ∠Q + ∠R = 180°  (Angle Sum property of triangle)

⇒ c + ( a + b) = 180°

⇒ c + 120° = 180°  (from equation i)

⇒ c = 60°

Now, from equation ii, a – c = 30°

⇒ a – 60° = 30°

⇒ a = 90°

Also, from equation i, a + b = 120°

⇒ b + 90° = 120°

⇒ b = 30°

Therefore, the angles of the triangle will be 90°, 30°, and 60° respectively.