Comparison of mathematics textbooks between Indonesia and Singapore is one way to assess the educational process. This article provides insight into how mathematical concepts are taught and applied in problem-solving in each country. The study provides knowledge about how mathematical concepts are constructed by teachers and students and implemented in problem-solving between countries. This study aims to compare task designs in high school mathematics textbooks between Indonesia and Singapore based on the type of task, technique, technology, and theory used, with a focus on cubes and cuboids. The comparative analysis of the two books uses praxeological theory, the main construction of Didactic Anthropology Theory, with reference to epistemological model (REM) model analysis. The research results show that there are differences in the approaches, methods, and habits used in task design in the two countries. The techniques, technology and theories found in the two task designs show that Indonesian mathematics textbooks use more verification and drawing up conclusions which are influenced by perceptual techniques. Meanwhile, the task of designing Singapore's mathematics textbooks involves more direct investigations into forming students' knowledge through physical and operational techniques. The techniques, technology, and theories used in both designs influence the number of learning obstacles. Epistemological constraints occur in Indonesian textbooks and only a few in Singapore textbooks. These findings provide insight into how to build mathematical knowledge for students through good assignment design based on a country's educational character.