This study aims to describe the adaptive reasoning abilities of students in SMP Negeri 5 Purwokerto viewed from student learning activeness on system of two-variable linear equations. This study uses qualitative research methods with the Miles and Huberman model which includes data reduction, data presentation, and conclusions. The subjects of this study were students of grade VIII H. The sample was obtained by purposive sampling technique. Students were categorized into three categories, namely students with high, medium and low learning activeness categories. Each category was selected by three students for research purposes. Data collection methods in this study used questionnaires, tests, interviews, and documentation. Based on the results of the study, it can be said that students with high learning activeness have mastered four of the five indicators of adaptive reasoning abilities precisely, namely the ability to make guesses, the ability to draw conclusions from a statement, the ability to check validity of an argument and the ability to find patterns from a symptom. Students with active learning are not yet able to master indicator in giving reasons about the answers given. Students with low learning activity only master one indicator of adaptive reasoning ability, namely the ability to find patterns from a phenomenon.