Hi, there are 1440 minutes in a day, and by extension 2880 minutes in two days (time is one of the few statistics common to the whole world, and the GMAT expects you to know 60 seconds to a minutes, 60 minutes to an hour and 24 hours a day.
24*60 = 1440 minutes = 1 day
48*60 = 2880 minutes = 2 days
So, the number of minutes can be broken down into 2,880,000 minutes + 717 minutes earlier. The 2,880,000 minutes is an even number of days and can thus be ignored (2,880,000 minutes earlier is EXACTLY the same time as right now), and we only need to consider the 717 minutes earlier. If 1440 minutes is a day, then 720 minutes is half a day. So 717 minutes is three fewer than half a day earlier.
At 6:27 in the evening, half a day earlier would be 6:27 am. But it's three minutes less than half a day, so we need to add those three minutes to 6:27 to account properly, which yield 6:30 am.
Answer is D