To apply MECE to your problem-solving, you need to follow four steps. First, you need to define the problem statement, which is the main question or issue that you are trying to solve. The problem statement should be specific, measurable, actionable, relevant, and time-bound. Second, you need to develop a problem-solving approach, which is the overall framework or logic that guides your analysis and solution. The problem-solving approach should be based on the problem statement, the available data and information, and the client's objectives and constraints. Third, you need to create a MECE issue tree, which is a visual representation of the problem-solving approach. The issue tree should start with the problem statement as the root, and then branch out into subproblems and hypotheses as the nodes. The issue tree should be MECE, meaning that each node should be mutually exclusive and collectively exhaustive with respect to its parent node. Fourth, you need to test and validate your hypotheses, which are the possible answers or explanations for each subproblem. To test and validate your hypotheses, you need to collect and analyze data and information from various sources, such as interviews, surveys, reports, or databases. You should use both qualitative and quantitative methods, and compare your findings with your expectations and assumptions.