This study developed a computer-assisted mathematical problem-solving system in the form of a network instruction website to help low-achieving second- and third-graders in mathematics with word-based addition and subtraction questions in Taiwan. According to Polya's problem-solving model, the system is designed to guide these low-achievers through the parts of the problem-solving process that they often ignore. The situations of verbal questions are visualised to walk the students through the course of thinking so they can solve the question with proper understanding of its meaning. We found that the mathematical problem-solving ability of experiment group students was significantly superior to that of control group students. Most of the participants were able to continue the practice of solving word-based mathematical questions, and their willingness to use the system was high. This indicates that the computer-assisted mathematical problem solving system can serve effectively as a tool for teachers engaged in remedial education. (Contains 7 tables and 8 figures.)