The purpose of this study is to examine how young adults and pupils use their metacognitive abilities such as cognitive strategies and self-checking during the mathematics problem-solving process. The study group consisted of 12 young adults selected from three different faculties in a foundation university and 32 pupils from public and privateK-12 schools, Istanbul, Turkey. Multimodal mixed-methods design was employed, where participants were asked to think out loud while solving ten mathematical problems. The experimental process was recorded with the use of eye-tracking, which was utilized to evaluate the active use of metacognitive sub-skills. The findings from the experimental process revealed that there is a significant difference between the amount of reflection of young adults’ and pupils' cognitive strategy and self-checking skill levels on their responses to mathematics problem solving process in favor of pupils.