We present a summary of a study carried out with students of the first year of Bachillerato
(the first of two pre-university non-obligatory secondary education courses in Spain) to
determine and analyse some of their errors and difficulties in learning inequalities with the
aim of improving the teaching-learning process of this topic. The study was based on
work on the initiation to algebra, in particular on the observed difficulties and errors
relative to algebraic skills.