<![CDATA[This study analyzed Grade X students' errors in solving mathematical literacy problems involving systems of linear equations in three variables (SPLTV, the Indonesian abbreviation) using Newman's procedure and identified factors associated with those errors. A descriptive qualitative design involved 57 students from three schools in Banda Aceh and Aceh Besar: SMAN 15 Banda Aceh (n = 20), SMAN 1 Kuta Baro (n = 17), and SMK SMTI Banda Aceh (n = 20). Data were collected through three written literacy tasks, interviews, and documentation; interview participants represented upper, middle, and lower within-school performance strata. Written responses were coded into reading, comprehension, transformation, process-skill, and encoding errors, while interviews clarified the reasoning behind observed errors. Across 171 student-item responses, transformation errors were most frequent (44; 25.7%), followed by encoding (42; 24.6%), comprehension and process-skill errors (36 each; 21.1%), and reading errors (15; 8.8%). Interview evidence indicated difficulties in converting contextual information into equations, applying elimination or substitution accurately, maintaining calculation precision, and expressing a contextual final conclusion. The findings suggest that instruction on three-variable linear systems should explicitly scaffold mathematical modeling, procedural verification, and interpretation of final answers rather than focusing only on algebraic computation.]]>
