Gemma has hiked a total of:
2 1/2 miles/hour × 3 hours = 7 1/2 miles
To find how far she is from the end of the trail, we can subtract the distance she has hiked from the total length of the trail:
11 3/8 miles - 7 1/2 miles = 3 7/8 miles
Therefore, Gemma is 3 7/8 miles from the end of the trail.