Situmorang, Ruth Sahana, Nahor Murani Hutapea, and Armis. “Development of Problem-Based Learning Materials on Linear Programming to Facilitate students’ Mathematical Problem-Solving Skills”. Jurnal Absis: Jurnal Pendidikan Matematika dan Matematika 7, no. 1 (August 30, 2024): 1–11. Accessed December 17, 2025. https://ojs-staging.upp.ac.id/index.php/absis/article/view/2339.