The current article presents the results of a study that aimed to analyze the difficulties faced by eighth grade students when learning to solve algebraic problems based on linear equations with one unknown variable. The participants were learners with low average performance in mathematics at a high school in Heredia. The research followed a naturalistic paradigm and the case study method with a qualitative approach. Different techniques like class observations, questionnaires to students, non-structured interviews to teachers and interviews to the learners were applied. The research helped to identify the main causes of difficulty when learning to solve algebraic problems. Some of the causes that were identified are affective aspects, lack of previous knowledge, poor relational understanding, fatigue, diversion, reading deficiencies and misunderstanding of terminology.

The calculation of the velocity of a continuous GNSS observation station represents a key input in modern surveying. The act of determining the position of the GNSS stations involves daily which can establish the time series of stations, based on which information can be influenced by phenomena affecting the performance thereof. This article is a description of the algorithm of the least squares adapted and applied to the determination of the velocity components of continuous observation stations. Furthermore, this algorithm is applied for calculating the speed of ETCG station belonging to the Geocentric System for the Americas (SIRGAS).

"MATEM" is a university outreach project. Among its objectives is to improve the mathematics education at the high school level and to accomplish it public universities work together with high school´s teachers and students. The study´s aim was to research various aspects of MATEM Project to order to evaluate its development and consider recommendations for making decisions. This paper summarizes the perceptions of high school students enrolled during 2012 in courses Precalculus and Calculus, moreover the opinion of mathematics teachers. The main results were that MATEM is an academic activity attractive for math teachers and student population from different regions of the country, although sometimes are not available the necessary conditions to develop it in their respective institutions, to have passed a university course, get more practice for the standard test at the end of high school, increase their math skills and prepare for college courses were the aspects that motivate students to enroll in the project, however the development of reasoning skills and abilities were more frequently pointed by respondents.