Explanation:
I don't see the tree, and have no clue what A, B and C are representing there.
I can tell you how to at least start thinking :
23 purple went fishing.
14 did NOT catch a perch. that means 23-14 = 9 DID catch a perch.
2 of these 9 did not catch a catfish. that means 9-2 = 7 DID catch a catfish.
3 people did not catch neither a perch nor a catfish.
that means from the 14 people not catching a perch 3 did not catch a catfish either. but that means the other 14-3 = 11 of these people DID catch a catfish.
so, it seems the people caught only 2 types of fish : perch and catfish.
of the total 23 people 9 caught at least a perch.
of these 9 people 7 caught also a catfish (so, a perch and a catfish), and 2 only caught their perch.
of the originally 14 remaining people 3 did not catch anything.
the other 11 did catch a catfish and nothing else.