There is a simple method, assuming that a=b=c=d= 1, which can satisfy 3 (a-1) 5 (b-1) =1,3 (C- 1) 5.
Then a=b=c=d= 1 becomes the above five 3a? 5b，3c？ 5d, 3×5, (a- 1)(d- 1), (b- 1)(c- 1) got the results: 15, 15,/.
Because the title has explained that two people with the same number are friends, so it can only be 0 and 0!
If it is the first few, it is three people, haha, I am a genius!
Adopt me!
In other words, what level of topic is this!