∠RMN = 90° (angles in a semicircle is a right angle)∠SRN = ∠RMN + ∠MNR (ext. angle of a ∆ is equal to the sum of two opp. int. angles)⇒ 5x + 20 = 90 + x⇒ 5x - x = 90 - 20⇒ 4x = 70
x = 704
= 17.4°
therefore, 2x = 2×17.5 = 35°