Hey! When it specifically states room temperature, we know that Substitution is going to be favored, however if it states that heat is involved then we know that the reaction is going to favor more Elimination. Also just to be certain, I would also spark a conversation with your professor to make sure that there isn't any other special circumstances that they like to teach that favor only Substitution. It never hurts for them to see your interest and get to know who you are as well!
I hope that clears it up and you are able to get more of these problems correct in the future :). Good luck!