Total number of groups of 3 students:
3∗2∗137∗36∗35=7770
In groups that do not meet the condition of the task, there will be 1 or 2 enemies
Number of groups with one enemy:
8∗2∗129∗28=3248
Number of groups with two enemy:
2∗18∗7∗29=1044
The number of groups corresponding to the condition of the problem:
7770−3248−1044=3478
Answer: 3478 concurrent student triples
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