This book presents approaches to answer the fundamental questions of "What to do?" and "How to do it?" that are at the center of all decision-making problems. The authors cover the essential topics including notions and fundamental concepts of fuzzy sets, models of multiobjective decision-making, the classical approach to dealing with uncertainty of information, and more. Different parts of the book provide original and non-trivial results, such as "harmonious solutions" in multiobjective problem-solving, construction and analysis of X, F> models, results aimed at generating robust solutions, and more. Finally, the book provides numerous representative applications, including acting real applications related to results of numerous industrial projects developed by the authors.