On several occasions, it has been shown that pupils and students have difficulties in solving tasks with graphs, but also in solving the problems with everyday life context, especially if they do not often meet this kind of problems. Unfortunately, in teaching of mathematics and physics there is still great emphasis on mastering certain procedures, but little attention is given to the application of acquired knowledge and skills in everyday life. The main goal of this diploma thesis was to investigate the pupils' and students' understanding of graphs as an important source of information. We constructed a test consisting of nine problems with graphs related to daily life that were used in the PISA survey in 2012. Beside the standard testing of students and pupils, and measurements of eye movements of students during problem solving, the participants had to explain their answers which helped us to determine their strategies in problem solving and recognize the difficulties they encounter in the process. The results showed that there was no statistically significant difference in accuracy in solving the test between the students studying at the Faculty of Science and students of other faculties at the University of Zagreb who voluntarily participated in this study. There was also no difference in accuracy between the students and the first year pupils of a general type gymnasium in Zagreb, as well as no differences in their strategies. By measuring the eye movements, we determined the time needed to solve problems and analyzed to which parts of the problems the participants paid more attention and whether it helped them to solve the task. The results suggested that the participants who correctly solved the problems focused their attention more to the areas with information relevant for problem solving. Finally, we determined how many of the students experience anxiety related to mathematics, how it is related to their grades and test results. We can conclude that in the teaching of mathematics it is necessary to include more examples from everyday life to strengthen the mathematical knowledge and to connect it better with other areas. This would also help students to develop a positive attitude towards mathematics and to be able to apply mathematical concepts to new situations.