We know that :
⊕ Sum of the three angles in a triangle should be equal to 180°
Given : Angle BAC = 50° and Angle ABC = 75°
⇒ Angle BAC + Angle ABC + Angle ACB = 180°
⇒ 50° + 75° + Angle ACB = 180°
⇒ 125° + Angle ACB = 180°
⇒ Angle ACB = 180° - 125°
⇒ Angle ACB = 55°
