Did anyone teach you how to apply this theory by your teacher ?

           were -> thì QKĐ : (?) Did + S + Vo

              teach + O + how to + Vo : dạy ai đó làm gì 

Don't let the children tease the dog

           let ( + O ) + Vo : để cho ai đó làm gì

What have you done to help the poor in this city?

            have been -> thì HTHT : (?) Wh_word + have/has + S + V3/ed

Where did the pirates use to hide the treasure in the old time?

             use + toV

EKI2k7