Michelle Mitchell presented a talk about workplace drug problems in our boardroom.
Revise the sentence
The problem here is “in our boardroom”. It is a place, it must belong to a verb or a noun here. To which one does it belong? It is normally taken with the last word before it that can take it. In this sentence, it must be “drug problems [that are] in our boardroom”. Are these drug problems actually in the boardroom? I think not: “in the boardroom” belongs to “presented a talk”: the talk was presented in our boardroom. The drug problems are somewhere else.
You see what’s wrong here? The adjunct “in our boardroom” is in the wrong place: it should go after “talk”, to make sure that it belongs to “presented a talk”, not to “drug problems”.
I understand. 
I am learning so much!