The purpose of this study aims to investigate the errors classes occurred by the Preparatory year students at King Saud University, through analysis student responses to the items of the study test, and to identify the varieties of the common errors and ratios of common errors that occurred in solving inequalities. In the collection of the data, the researcher employed the open-ended questions test consisted of nine items distributive on three types of inequalities (linear, involve absolute value and fractional). In the data analysis, descriptive analysis method was used. The result showed that some students had some misconceptions and misunderstanding in solving types of inequalities. The greatest common errors ratio was (20%) in solving linear inequality come from the class "Errors in basic algebraic operations and deletion." But the ratio (22%) were the greatest common errors ratio in solving fractional and involving absolute value inequalities come from the class errors in absent meaning of inequality.