The aim of this study produces mathematics instructional materials, on linear equations and inequalities one variable with inquiry methods that valid, practical, and effective criteria in terms of student achievement and self-confidence. This study is developmental research. It is adapted from Reiser & Dempsey models. The research through several phases: analysis, design, development, implementation, and evaluation. The instructional materials is consists of syllabi, lesson plans, student sheet activity, and daily tests. The results showed that is the valid criteria valid, practical, and effective. Validity of development product is determined by the expert validation, the practicality is determined by the assessment of teachers, and students, while the effectiveness in terms of student achievement and self-confidence. Achievements of students achieving an average of 76.9412 beyond the KKM 70, while the confidence of students from 55.88% to 82.35% on minimal good category.