Answer:
20°
Step-by-step explanation:
A triangle = 180°
∴ 180° -120°-40°
=20°
The Angle Sum Property of a triangle gives that the sum of the internal angles of a triangle is equal to 180°.
Hence,
⇒ ∠A + ∠B + ∠C = 180°
⇒ ∠A + 120° + 40° = 180°
⇒ ∠A + 160° = 180°
⇒ ∠A = 20°
