Problem solving skill is a basic skill that students should acquire both in mathematics education and their daily lives. This research aims to examine fourth-grade elementary school student skills in solving four-operation problems prepared in different structures according to the situation of the unknown. In this research, on the one hand, students' success in solving four-operation problems prepared according to the unknown (initial, change, and final unknown) was examined, and on the other hand, problem solutions were analyzed according to Polyo's problem solving steps. This research is a survey model from quantitative research methods. The sample of this research consists of 150 students studying in the fourth grade of two public primary schools in Amasya city center in the 2021-2022 academic year. The "Problem-Solving Achievement Test" developed by Bayar (2022) was used as a measurement tool in this research. Based on the findings obtained because of the analysis of the data; it was determined that students were significantly more successful in problems with unknown outcomes than in problems with unknown both initial and change. Besides, although the students were successful in the step of understanding the problem in the problem-solving steps, they were less successful in the steps of planning, executing the plan, and controlling the plan, respectively, compared to the step of understanding the problem. A positive relationship was found between all the variables in this research, albeit at a moderate and low level. It would be beneficial to revise the problems in the textbooks and classroom practices within the framework of the results.

This study mainly aims to identify the correlations between school principals’ toxic leadership characteristics and teachers’ perceptions of mobbing. Beside its fundamental purpose, this study also aims to identify the levels of school principals’ toxic leadership characteristics and of teachers’ mobbing perception and whether or not those levels differ according to demographic and occupational properties. The study uses the relational survey model and quantitative design. The sample was composed of 455 teachers teaching in schools in Çanakkale city centre and in the county of Çan in 2023-2024 academic year. The research data were collected with the Demographic Information Form, Mobbing Scale and Toxic Leadership Scale. Percentage analysis, frequency analysis, regression analysis, correlation analysis, Mann Whitney-U test, Shapiro-Wilk test, Kolmogrov-Smirnow test and Kruskal Wallis-H test were used in analysing the data. As a result, teachers’ perceptions of school principals’ toxic leadership characteristics and their perceptions of mobbing were generally found to be at medium level. In addition to that, teachers’ perceptions of toxic leadership differed significantly according to gender, level of education and school where they taught. On the other hand, positive and significant correlations were found between principals’ toxic leadership characteristics and teachers’ perceptions of mobbing. As a result, school principals’ behaviours and performance can be monitored and evaluated, and administrators can be offered training by giving feedback in relation to their toxic leadership and mobbing behaviours.