Pedagogical content knowledge is a key role the success of teachers learning in classroom. This study aims to: 1) analyze teacher's knowledge of students' mistakes and difficulties in solving linear equations, 2) describe the instructional strategies used by teachers to eliminate students' mistakes and difficulties. The subjects of this study were two novice teachers with two-year working period, each of whom taught at the seventh grade junior high school with different students' math abilities. Data collection is conducted by open questionnaire and interview. The results showed that both teachers have knowledge of students' mistakes and difficulties in solving linear equations. However, the teacher's learning strategy in helping students to eliminate students' errors and difficulties is different. Thus it can be concluded that the teacher's knowledge of the errors and difficulties students can help teachers in determining appropriate learning strategies to present learning materials.