Quote Originally Posted by pushvv View Post
и что? собрание
р чего? собрания
д кому? собранию
в что? собрание
т чем? собранием
п о чем? о собрании

Стало быть винительный (accusative) падеж.
Russians always use these questions to determine case. I have no idea how it works, and numerous attempts at explaining it to me have failed.

Does anyone have an explanation that I might be able to understand?

Thanks in advance.