This study explored problem-solving in middle school, focusing on how students use tools to solve problems when working on mathematical tasks. The Problem-solving Assessment, Diagnosis, and Remedial Instruction (PSADRI) system was designed and developed as an individual teaching tool to support mathematics education, foster students’ ability to solve problems. A quasi-experimental design was conducted during five weeks. The 153 students who participated in this experiment were divided into an experimental group (86 students who used the PSADRI system) and a control group (67 students who received traditional instruction). The results revealed that the students who used the PSADRI system achieved greater learning performances in mathematics and improved problem-solving ability compared with the students who received traditional instruction. Using the question-guided training function in the system, the students in the experimental group used the drill-and-practice strategy to solve math problems step by step to achieve mastery in mathematics learning. Moreover, the students’ learning performance in the experimental group was enhanced and their problem-solving ability was improved. The major contributions of this study were the improvement in middle school students’ academic achievement in mathematics and problem-solving ability and enhanced interest in mathematics learning via the PSADRI system, an individual teaching system.