Answer:
∠ ABD = 19°
Step-by-step explanation:
Since AB and BC are congruent, then Δ ABC is isosceles and the base angles are congruent, that is
∠ BAD = ∠ BCD = 71° , thus
∠ ABC = 180° - (71 + 71) ← angle sum of triangle
∠ ABC = 180° - 142° = 38°
DB is an angle bisector , thus
∠ ABD = 0.5 × 38° = 19°
