Coordinate geometry is an important part of mathematics. It helps students develop thinking, logic, and problem-solving skills. This study was conducted to test the effectiveness of the CORE learning model in promoting students' mathematical problem-solving skills when they learn the method of coordinates in a plane. Consequently, this study used mixed methods as a quasi-experiment with a non-equivalent control group design, with assessment tools including pre-test, post-test, classroom observation, and attitude survey. The data collected were quantitatively analyzed with JASP and qualitatively analyzed. The analysis findings demonstrate that the students in the experimental group performed better academically in terms of knowledge and problem-solving skills and had more optimistic learning attitudes. In particular, a correlation test was performed on the pre-and post-test scores of the experimental group. It showed that with a correlation level of 0.810, according to the Hopkins reference table, the scores of the students in the experimental group were higher than those of the control group due to the effectiveness of the CORE learning model in promoting students' problem-solving abilities. In addition, the study identified certain limitations and proposed new research directions for the future.