In Engineering careers, the highest levels of academic neglect and delay are observed along the first years in which the subjects enrolled in basic training. Math skills are required not only in the area subjects but also in other subjects of that period. That’s why, as part of steps to improve retention of students in these careers, acquire significance the study of the difficulties that students show about these skills. This paper presents an analysis of the results of the a diagnostic questionnaire answered by freshmen to Engineering careers from Universidad Nacional de Mar del Plata. The questionnaire was developed to study some math skills related to specific topics in the Middle LevelEducation curriculum. Such skills were selected from shortcomings observed by teachers in basic science subjects and recorded in a survey. The analysis is based on theoretical guidelines given by the Onto-semiotic Approach of the Cognition and Mathematics Instruction, developed by Godino and colleague. The epistemic meanings of the skills assessed were compared with the personal meanings of the students. It was confirmed that there were difficulties in some math skills such as algebraic manipulation, clearing variables, solving proportionality problems and analytical resolution of basic trigonometric equations. The results constitute a contribution to make teaching activities aimed at overcoming these difficulties.