In general, chemical engineering has the aim to direct students in understanding the basic concepts of chemical engineering, fuel, and lubricating oil in the automotive field. One of the subjects is calculating octane numbers of gasoline which involve mathematical operations, which can cause anxiety to the learner. Therefore, a learning approach is needed that can reduce mathematical anxiety through problem posing. The application of problem posing aims to improve student learning outcomes. Before being applied, lesson study (plan-do-see) was carried out. The samples were taken using cluster sampling techniques,