Perceptions of complexity from the Scientific Holistic Thinking Perspectives included resolving the complexity dichotomy. Problem-solving like most other things is based on a set of assumptions. The most important use of systems thinking in problem-solving is in decision-making. This chapter deals with problems and problem-solving. It shows how to deal with ill-structured, wicked and complex problems using iterations of a sequential two-stage problem-solving process. The traditional problem-solving approach manages large and objectively complex well-structured problems by breaking them out into smaller and simpler problems. From the perspective of the problem-solving paradigm of project management, the standard approach to evolving a solution can be reworded to become ‘an evolutionary approach to remedying the undesirability in a situation by turning an ill-structured problem into a number of well-structured problems. The first problem-solving process in the multiple-iteration problem-solving process remedies a research problem using an adaptation of the scientific method.