In an interconnected world, decision-making has become increasingly complex and critical. This complexity is driven by a multitude of interconnected decisions and the rapid evolution of technologies and markets. Managers must navigate this landscape by quickly evaluating numerous options and selecting the optimal course of action, particularly in areas such as investment, financing, and production processes. Decision theory, a subfield of operations research, offers valuable insights and tools to address these challenges. By providing the theoretical foundations and practical case studies, this work gives a deeper understanding of the decision tree procedure to support decision-making.