Is it 16/21?

There can be only 2 groups possible among 7 of them:

Group1 : ABCD - Have of them exactly 1 friends

Group2 : EFG - Have exactly 2 friends

P(Both NOT friends) = 1 - P(Both friends) = 1 - [ P(two friends are from Group1) + P (two of them are from Group2)]

P(two of them have exactly 1 friend) = 4/7*1/6 -- Choose any of the 4 friends from Group1 and then choose HIS only freind

P (two of them have exactly 2 friends) = 3/7*2/6 -- Choose any of the 3 friends from Group2 and then choose one of his 2 freinds

P(Both NOT freinds) = 1 - { 4/42+6/42} = 16/21.

I may be wrong....

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