Answer:
x = 40°
Explanation:
given Δ ABD is isosceles with AB = AD
then the base angles are congruent , that is
∠ ABD = ∠ ADB = 25°
given ABC is a straight line then the 3 angles on it sum to 180° , that is
∠ ABD + x + 115° = 180°
25° + x + 115° = 180°
x + 140° = 180° ( subtract 140° from both sides )
x = 40°