We haven't seen Tom since he left school __________________________________.

`=>` We last saw Tom when he left school 

`=>` The last time we saw Tom was when he left school 

`=>` S + hasn't / haven't + Vpp + since + mốc thời gian 

`=` S + last + Ved / V2 + O + when + mốc thời gian 

`=` The last time + S + Ved / V2 + O + was + when + mốc thời gian 

`-` Tạm dịch : Chúng tôi đã không gặp Tôm từ khi anh ấy rời trường