Hi Silvia,
As a general rule, if you are asked to find the 'least' that a value can be, maximize all the other values. Conversely, if you're trying to find the 'most' that a value can be, minimize all the other values.
In this case, to find the least possible score that a team could have earned, maximize the other teams' scores. In this case, we're told that the max for any team is 6 points. So the question can simply be restated as "if team A and team B earn 6 points each, what will be team C's score?"
To represent this clearly, a table would work. Essentially team A can earn 5 (1st place finish) and 1 (5th place). Team B can earn 4 (2nd place finish) and 2 (4th place). Therefore team C will have a member finish 3rd place and earn 3 points. The other team C member will finish last and earn no point.
The least possible score for a team is 3 points. The answer is
D.
An illustration (table) and a video solution are available at
GMATPrep Question 1580. To practice similar questions, set topic='Functions & Sequences' and difficulty='500-600' in the Drill Engine.
Hope this helps,
-Patrick