Answer:
(a) 3
(b) 28
(c) 66
(d) 190
Step-by-step explanation:
For any group of people of size 'n' people, the number of different two-person relationships, if order does not matter, is given by:
[tex]N=\frac{n!}{(n-2)!2!}[/tex]
(a) For n = 3
[tex]N=\frac{3!}{(3-2)!2!}=3[/tex]
(b) For n = 8
[tex]N=\frac{8!}{(8-2)!2!} = 28[/tex]
(c) For n = 12
[tex]N=\frac{12!}{(12-2)!2!}=66[/tex]
(d) For n =20
[tex]N=\frac{20!}{(20-2)!2!} =190[/tex]