The phenomenon today in schools is that teachers rarely build student arguments but only accept students' answers. However, teacher activities that always make students 'arguments and support each solution and defend students' arguments without long debates are relevant and exciting to study. This study aims to explain and explore the promotion of mathematics teacher reasoning in tasks in the classroom. The author surveyed teachers who teach mathematics at the junior high level. This research is a qualitative descriptive study with an experimental research design, which begins with a survey of teachers who teach mathematics at the junior high school level in Maluku Province. First, the authors conducted initial observations for one month in several junior high schools in Maluku Province with the guide of the observation instrument for the promotion of teacher reasoning in learning. Second, the writer states that there are three groups of attractive teachers who can promote mathematical reasoning in each of their teachings based on indicators of teachers' mathematical reasoning. Third, the writer created the same math problems for the three teachers and observed how they built students' reasoning and evaluated their thinking efficiently. Finally, the results and surveys were carried out by triangulation with direct trials on seven classes at the junior high level. The results show how teacher actions promoting mathematical reasoning give generalizations or justifications. Teacher actions supporting precise rationale are discussed in more detail in this article.