Hi there! I'm from Vietnam and I want to help you this question! because my english is not good enough to explain to you, so if you dont understand what i said, you can ask me again until you know those meaning of this! Firstly, "trông"-it doesn't mean "in" in English, you can use "trông" like "trông thấy" (see) or "trông nom" (look after). And if you mean this meaning "in", I think you mentioned "TRONG" (It's not "TRÔNG") Secondly, "ở", "tại", "vào" - they have the same meaning. Of course, you must depend on context. Example: + I live in Vietnam :) means Tôi sống tại/ở Việt Nam + In 1989, .... means Vào năm 1989,.... + And "Vào vị trí" - I dont know how to explain to you :'( - But it means the racers (or athletes) are going to move in their position on the race. Finally, "TRÊN" means "on" not "in" That's it! I hope you understand what I tried to say! (Sorry about English and I really want to be your friend to help each other!)