Answer:
∠ AOB = 17.5°
Explanation:
∠ AOB + 110 + ∠ COD = 180 ( sum of angles in straight line )
∠ COD + 110 + ∠ COD = 180 ( subtract 110 from both sides )
∠ COD = 70 ( multiply both sides by 3 to clear the fraction )
4 ∠ COD = 210 ( divide both sides by 4 )
∠ COD = 52.5°
Thus
∠ AOB =
× 52.5° = 17.5°