Какое отношение надо вставить вместо *, чтобы получить пару взаимно обратных отношений: 1) 4: 9 и *; 2) 10: 3 и *; 3) 2/13 и *; 4) 3 1/4 и *?

They were eating a pie when I entered into the room.
I was playing football at 5 o'clock yesterday
He was speaking at the meeting while we did that work.
You were laughing at him .