This research is a quasi-experimental study with the following objectives: 1) To examine the effectiveness of cooperative learning activities using the TAI technique combined with activity-based learning on the topic of congruence for students at Roi Et Rajabhat University, aiming to achieve the 75/75 efficiency criterion. 2) To compare mathematical problem-solving abilities before and after implementing the learning activities. 3) To compare mathematical connection abilities before and after the learning activities. The sample group consisted of 24 students enrolled in the Number Theory course during the first semester of the academic year 2024, selected through cluster sampling. The research instruments included: 1) Four lesson plans for cooperative learning activities using the TAI technique combined with activity-based learning, 2) A subjective test measuring mathematical problem-solving abilities consisting of five items, and 3) A subjective test measuring mathematical connection abilities consisting of five items. The statistical methods used were mean, percentage, standard deviation, and the Wilcoxon Signed Rank Test. The research findings revealed that: 1) The cooperative learning activities using the TAI technique combined with activity-based learning achieved an efficiency of 80.83/78.85, which was higher than the specified criterion. 2) The students' mathematical problem-solving abilities on the topic of congruence were significantly higher after the learning activities at the 0.05 level of significance. 3) The students' mathematical connection abilities on the topic of congruence were significantly higher after the learning activities at the 0.05 level of significance.