In this paper we analyze the meanings of the "equal" sign as generated by sense production of the methods of substitution and comparison for solving problems and systems of equations of two unknowns. These methods are usually introduced through an extension process of the syntax and meanings recently learned by students in order to solve problems using linear equations with one unknown. Through this process some users were able to confer sense to the methods and thus generate the new meanings required. [For complete proceedings, see ED500860.]