Answer:
∠DBC = 40°
Step-by-step explanation:
∠5 = ∠3 + ∠4 = 180° - ∠6 . . . . relationship of angles at a transversal, vertical angles
∠3 = 180° - ∠1 - ∠2 . . . . . . sum of angles of a triangle
Then
∠4 = 180° - ∠6 - (180° - ∠1 - ∠2) = ∠1 +∠2 -∠6 . . . . substitute for ∠3
∠4 = 65° +60° -85° = 40°
∠4 = ∠DBC = 40°
