YOU SAID:
Who knew that you're good at math!
INTO JAPANESE
あなたが数学が得意だということを誰が知っていたでしょうか。
BACK INTO ENGLISH
Who knew you were good at math?
INTO JAPANESE
あなたが数学が得意だということを誰が知っていましたか?
BACK INTO ENGLISH
Who knew you were good at math?
You've done this before, haven't you.