It takes Greg 6 minutes to run a mile, and it takes Pete 8 minutes.

Since Greg will run s miles after s × 6 minutes and Pete will run c miles after c × 8 minutes, they both will finish running a mile at the same time when s × 6 = c × 8. Since s and c must be integers (they represent the number of miles finished) this question is asking you to find a common multiple of 6 and 8. The question asks for the first time they will finish running a mile simultaneously, so you must find the least common multiple. The least common multiple of 6 and 8 is 24, so in the context of the question, this would be 24 minutes. Therefore, the first time they will finish running a mile at the same time is 8:30 + 24 minutes, or 8:54 a.m. The answer is (D).