This study concerned itself with teaching and learning of the subject of mathematics. It was a base line study of individually adapted education according to the diversity of pupils. The study was grounded on aspects of the Curriculum Relation Model developed by Johnsen (2001, 2003 & 2007). The Model was used for presentation of related literature which included theoretical aspects and previous studies in the field of mathematics. It was also used as a main inspiration tool for further development of arenas and sub-arenas in the analysis and presentation of findings. The purpose of the study was to investigate how the teacher managed to teach mathematics to all pupils with different educational needs, which challenges the teacher met in this process and how the teacher overcame them. These questions were investigated through a single case study. The study was conducted in the purposefully selected primary school with one teacher in the third grade class taken from a primary school in the Canton of Sarajevo, Bosnia and Herzegovina. In order to get in-depth information from different angels, the study included observation, interview and texts and materials analysis as research methods. The findings obtained showed that assessment was a crucial pre-requisite for adapting teaching to the diversity of learners. The teacher followed the mathematics curriculum prescribed by authorities and she used time in deciding how to teach. Even though the long-term objective was the same for all pupils, the teacher meant that pupils should progress at their individual pace of learning. Thus, the teacher adapted teaching plan and program according to the diversity of the pupils. Regarding teaching strategies, the teacher used a variety of methods, classroom organization and teaching materials. The principle of scaffolding and direct engagement of pupils in class activities was evident during the lessons. The teacher and the pupils exchanged guiding roles of teaching and in that way peer support was expressed fully, as well as balancing of classroom organization. The teacher also conducted individual teaching, extra teaching and out of school activities with the purpose of giving additional support to learning. Findings regarding care and communication showed that the teacher paid attention to pupils’ emotional and psychological needs. The study also revealed that the teacher met some challenges that she experienced as dilemmas and problems. The teacher expressed dilemmas regarding all aspects of teaching-learning process and found problems within frame factors, but tried her best to confronted most of them. The Curriculum Relation Model (Johnsen 2001, 2003 & 2007) is proposed as a possible solution and base for planning, practicing and assessment of teaching-learning process in mathematics.