Since 2003, international project PISA evaluates 15-year old students in solving problems that include "decision taking", "analysis and design of systems" and "trouble-shooting". This article presents the results of a pilot research conducted with 215 students from first to fourth grade of a high school in Sarajevo (Bosnia and Herzegovina). The students, in an imaginary, real-life like scenario, had to advice a bus company about number of buses needed for operating a 24-hour service between two cities. Research instrument was structured in a way, which permits exploring how students deal with a "complex problem" (in PISA terminology it would be problem type "analysis and design of systems") in real-life setting. Negative research results show that students mainly (1) use either verbal or visual reasoning mode; (2) have poor "sense-making" approach in analyzing a simple dynamical system and (3) have underdeveloped an important competency for working in knowledge-based economy (decision-taking based on evidence and arguments). A positive result is that majority of students found interesting the problem in question. Some brief recommendations about the presence and role of "complex problem" in physics teaching are offered in conclusions.