The aim of the thesis was through a new analysis of interviews with teachers of mathematics, to describe didactic practices used by teachers while teaching selected topics (namely, proportions, linear equations, divisibility, percent, symmetry, Pythagorean theorem ) and compare them with the practices reported in textbooks and other literature. First, teaching methods, teaching forms and the mechanism of concept development by M. Hejný are given. Based on the analysis of more than thirty interview, it was found that teachers use the usual didactic practices but also create their own methods and procedures. These methods and techniques are provided for each critical issue separately in the fourth chapter of the thesis. Furthermore, the content analysis of selected textbooks is given for each topic. Identified practices of teachers which they use in their teaching practice, form the result of my work.