The aim of this research is to use the decision-making tree in order to give the meaning for the classification of some activities done during the realization of the math subject lesson. Actually, the aim is to identify which activity is more important in achieving the objective of the lesson and at the same time, which one has bigger impact in achieving the final results on the math course.

In total we have used 22 variables divided into three different groups: the first one is about some activities concerning the beginning of the lesson, the second groups are the variables about the continuation of the lesson and the third groups are the variables concerning the exercises and assessment. For all of these three activities, we have chosen the averages of the answers for every group separately.

In this research are shown the results gathered from 48 randomly chosen students of the Faculty of Business Economics at the SEE-University in Macedonia, who have attended the math subject on the winter semester of the year 2016.

For the construction of the decision-making tree, we have used the ID3 algorithm by using the Weka software.

We have found that the root of the decision-making tree is the attribute concerning the activities taken at the exercises and assessment. This attribute at the same time is the most important attribute from all 4 attributes.

teaching practice, decision tree, ID3 algorithm, Weka software.