This article outlines the methods of a teacher of mathematics who works with a class of students with language disorders related to autism. By adopting the theoretical framework of the Dual Approach (ergonomics and didactics) and Maturanian epistemology, we show how an analysis of language interactions allows for a better understanding of teaching practices and their influence on the mathematical activity of students. We explore the nature of the language interactions, both verbal and non-verbal, within a specific learning project, when it comes to reinvesting, in a non-explicit way, basic mathematical objects. Our analysis highlights the richness of a practice in which the teacher proposes different types of help to trigger the mathematical activity of her students.