Contribution of the activity of problem situations in addition and subtraction as an educational object for Middle School students. Research, Society and Development, [S. l.], v. 8, n. 9, p. e10891264, 2019. DOI: 10.33448/rsd-v8i9.1264. Disponível em: https://ojs34.rsdjournal.org/index.php/rsd/article/view/1264. Acesso em: 28 jun. 2025.