Equation rearrangement is an important skill required for problem solving in mathematics and science. Eye movements of 40 university students were recorded while they were rearranging simple algebraic equations. The participants also reported on their strategies during equation solving in a separate questionnaire. The analysis of the behavioral and eye tracking data, namely the accuracy, reaction times, and the number of fixations, revealed that the participants improved their performance during the time course of the measurement. The type of equation also had a significant effect on the score. The results indicated that the number of fixations represents a reliable and sensitive measure that can give valuable insights into participants' flow of attention during equation solving. A correlation between the number of fixations and participants' efficiency in equation solving was found, suggesting that the more efficient participants developed adequate strategies, i.e. "knew where to look." The comparison of eye movement data and questionnaire reports was used for assessing the validity of participants' metacognitive insights. The measures derived from eye movement data were found to be more objective and reliable than the participants' reports. These results indicate that the measurement of eye movements provides insights into otherwise unavailable cognitive processes and may be used for exploring problem difficulty, student expertise, and metacognitive processes.