Hi, I would try to equate to a real world situation to confirm the way that originally thought about the wording. In this case, (and I usually do this for ordering ones) I think about days of the week. Here, we are concerned with things happening exactly three days after another.
So, I would ask what is exactly three days after Monday. Since Thursday is three days after Monday we have M _ _ T, and we can then sub in G and S.
