Siahaan, Meiva Marthaulina Lestari, et al. “Hypothetical Learning Trajectory: To Determine The Solution of Linear Equation System in Elementary Row Operation”. Mathline : Jurnal Matematika Dan Pendidikan Matematika, vol. 8, no. 1, Aug. 2021, pp. 246-55, doi:10.31943/mathline.v8i1.379.