Following presents left to unwrap:one from A, three from B and three from C. How many ways to arrange these presents in the form of a circle if no two presents from person B can be placed one next to another?

total 7 presents can be used to form circle in (7-1)! ways = 6! ways

out
of which 3 gifts of can be together so we need to find the way in
which all the gifts can be placed next to each other = (5-1)! = 4! ways and 3 gifts can arrange themselves in 3! ways.

and 2 gifts can be considered as 1 and can be arranged in = (6-1)! = 5! ways and 2 gifts can arrange themselves in = 2! ways