In order to solve for the angle \( b \) in a triangle, we need to clarify the setup. If angles A, B, and C are part of the triangle (with A = 115°, B = 120°, and C = 75°), it immediately raises a question because the sum of angles in a triangle must equal 180°.
However, it appears there may be some confusion in your question, as it lists a fourth angle \( D \) without context. If we consider angles A, B, and C as part of a triangle, we can check the validity of those angles:
A + B + C = 115° + 120° + 75° = 310°
Since 310° exceeds 180°, these angles cannot all belong to the same triangle. As such, we cannot find an angle \( b \) without further clarification on the relationships or constraints involving these angles.
If you meant to ask for a specific angle related to another triangle or context, please provide additional details so I may assist you accurately.