Answer:
22.5°
Explanation:
are two isosceles triangles, the left one is right and has 1 angle of 90° and two congruent angles, the sum of the internal angles (triangles only) is 180°, therefore 180 - 90° = 90° (sum of the angle ABD and BDC) we divide by two and we find the value of the single angles, 90:2=45°.
Then pass to AC which is a straight line, value 180°, subtract 45° and you have 135° of the angle BDC, subtract 135 from 180 and you have the sum of the two congruent angles (DBC and BCD) , finally divide by two and you have 22.5° which is the your answer. I hope I was clear.