Delete worlds on the note (tablet)

I can't get rid of or delete any mine craft world because when I click x and then ok, it is still there and I have tried all the worlds and it turn out that I can only delete the worlds that I have only made that day. I am wanting to delete u to 3-4 world but they wont let me. And I don't know what to do. It is on the note. (A tablet).