Analysis of Epistemological Barriers in Students’ Problem-Solving of Basic Algebra in Junior High School through the Didactical Design Research (DDR) Approach. riemann [Internet]. 2025 Dec. 31 [cited 2026 Apr. 18];7(3):296-30. Available from: http://journal.sanagustin.ac.id/index.php/reimann/article/view/130