  This article reports the argumentation work of a group of trainee mathematics
teachers in an experiment carried out in a virtual class (due to the emergence
of COVID-19) during 2020. They worked with a task on fractions in an online
assessment system with questions with random parameters and infinite possible
correct answers. This was followed by a discussion of the strategies and the
justifications, arguments and validations of these strategies and other
conjectures that emerged. This article analyzes this work from a qualitative
approach using the Mathematical Working Space as a theoretical framework. The
results show that the discussion work led the trainee teachers to find
interpretations for the algorithms processed by the computer, enhancing
epistemic discourse and argumentation in the context of the use of
technological artifacts. In turn, the same discourses allowed the future
teachers to instrumentalize the processes to be used in new tasks.
