The book deals with some interesting topics, which are both approached from theoretic and pragmatic point of view. The first chapter focuses on the existence of guaranteed optimum strategies and on the existence of equilibrium points. The second chapter is devoted to the sequential decision problem and provides an overview on optimum behavior for the decision makers which take part in the decision process. There are analyzed optimum criteria of cautious strategic behavior, hazardous strategic behavior and the cooperative case; for each particular situation we analyze the existence of optimum trajectories. Chapter three aims to solve an essential problem within the context of reliability theory - the determination of failure moments for a complex system which is made of multiple components. Practically, the failure moments are determined as equilibrium points. Chapter four, deals with the dependency between reliability and electric energy consumption. This relationship is analyzed within the framework of a very general case, starting form the analytical expression between reliability and the normalized consumption of electric energy.