Answer:
6
Explanation:
1 shook 2,3, and 4's hands
2 shook 3, and 4's hands
3 shook 4's hands
4 already got his hand shaken by everyone
1-2, 1-3, 1-4.
2-3, 2-4
3-4
(Anyone feel free to correct me. I'm not amazing at math just trying to help out.)
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