Chapter 7 is algebraic expression, which is parallel to intersection relation. Triangular congruence, axial symmetry, probability. According to the relevant materials of junior high school mathematics textbooks, we know that the seven chapters are algebraic, parallel intersection, relational, triangular congruence, axial symmetry and probability. The content of Beijing Normal University is slightly less than that of People's Education Edition, but it is much more difficult than that of People's Education Edition.