Answer:
x = 20°
Step-by-step explanation:
Since BD = CD then Δ BCD is isosceles and its base angles are congruent, so
∠ CBD = ∠ BCD = 80° , then
∠ BDC = 180° - (80 + 80)° = 180° - 160° = 20°
∠ ADC = 180° - (80 + 60)° ← sum of angles in triangle
∠ ADC = 180° - 140° = 40° , then
∠ BDC + x = 40°
20° + x = 40° ( subtract 20° from both sides )
x = 20°
