This study explores students' use of mathematical objects in each problem-solving phase based on an onto-semiotic perspective. The subjects of this research are students who solve problems in different ways but all with the correct result. The first student uses organizational data by applying the concept of permutations. In contrast, the second student uses visual representation (making pictures) by applying the concept of filling in slots or multiplication rules. The results showed variations in the formation of mathematical objects in each problem-solving phase and indicators of activity using mathematical objects. The detail of students' work will be discussed comprehensively.