The study aims at (1) describing the mathematical communication at class VII junior high school in solving problems of the system of equations and linear inequalities of one variable, (2) analyzing the factors that cause students to correct problems in system material and linear inequalities of one variable. The data were collected in the form of text, images and words. The study adopted the descriptive research design based on qualitative data collected from the participants who were selected using purposive sampling model. Subjects were selected by selecting one student for each category with high, medium, and low ability, in total three participants. On the subject of high ability, in order to determine the participants, the criteria were writing texts well, drawing well and the level of reflecting good mathematics as well. Medium ability subjects were supposed to meet the criteria in the aspects of writing well, although still relatively low. Low ability subjects on the criteria of aspects of writing and expressing mathematics, classified at a very low level. The factors causing the students' mathematical communication abilities were found to be the use of vocabulary and mathematical language, the students’ learning style and the ability to express their ideas.