To ensure the learning of mathematics, teachers must be able to analyse their students' mathematical practices when solving tasks, interpret the difficulties that students encounter, and decide how to manage students' difficulties. This competence in didactic analysis and intervention allows teachers to adapt their teaching to meet individual student needs. In this paper, we analyse how preservice teachers interpreted students' responses to a task involving the proportional determination of probabilities and understanding the sample space. We propose didactic strategies that help students overcome difficulties. The results revealed the difficulties some preservice teachers experienced in adequately interpreting student responses and making informed decisions to improve learning.