Mathematical and computational thinking (CT) are closely interrelated, yet CT integration into mathematics instruction remains limited. This study aims to analyze the effectiveness of the teaching process for straight-line equations in enhancing students' CT skills and to propose improvements based on the findings. A qualitative case study involved 32 eighth grade students and a mathematics teacher. Data were collected through classroom observations, CT-based tests, and in-depth interviews. The findings show that teaching was mainly based on direct instruction using habituation problem tasks, resulting in low student participation and underdeveloped CT skills. In particular, 75% of the students had difficulty with decomposition, pattern identification, abstraction, and algorithmic thinking, showing difficulty applying mathematics to CT problem-solving contexts. These findings suggest the need for instructional redesign: inquiry-based learning and technology integration to foster CT development. The study provides practical implications for improving mathematics instruction by promoting active learning approaches that enhance CT.