Answer:
130°
Explanation:
See the attached diagram. 
Given that ∠ ROS = ∠ TOU = 9x + 5 
Again, ∠ ROT = 13x + 15. 
Therefore, 13x + 15 + 2 (9x + 5) = 180 
⇒ 31x + 25 = 180 
⇒ 31x = 155 
⇒ x = 5 
Hence, ∠ SOT = ∠ SOR + ∠ ROY = 9x + 5 + 13x + 15 = 22x + 20 = 130° 
(Answer)