1. "What" stage: define the problem, describe the phenomenon, and clarify the content and scope of the study.
2. "Why" stage: analyze the problem, explain the phenomenon, and explore the root and influence of the problem.
3. "What to do" stage: propose solutions and effective countermeasures and action plans for the problems.
In practice, these three stages are not strictly separated, but intertwined and mutually supportive. In the process of thinking and solving problems, we need to iterate, modify and improve constantly in order to get an accurate, comprehensive and feasible solution.