Twelve linear algebra students were interviewed about the concept of a Solution of a System of Equations. The interviews were analyzed using APOS tools, in particular the ideas of Action, Process, Object and Schema, and Genetic Decomposition. The analysis of the interviews revealed several misconceptions of Solution. The analysis also revealed shortcomings of the questionnaire that was used in the interviews: It did not permit making a distinction between lack of knowledge and partial knowledge. Research tools were improved (questionnaire, GD, and suggestions for teaching materials) and prepared for the next cycle of research. [For complete proceedings, see ED489632.]