In the current context of educational reform, fostering students’ collaborative problem-solving skills and critical thinking through mathematics education has become an essential objective. This study aims to clarify the theoretical foundations for proposing a decision-making process based on group collaboration, while also developing illustrative teaching situations for the topic “Proportions” in Grade 7 to cultivate this skill among students. Using theoretical research methods, including analysis, synthesis, and systematization of relevant literature, the study has clearly identified the stages involved in learners’ decision-making processes within a collaborative mathematical learning environment. The findings provide a theoretical framework and useful reference materials for school teachers in designing learning tasks that foster the comprehensive development of students’ competencies.