The blue lake trail is 11 3/8 miles long. gemma has hiked 2 1/2 miles each hour for 3 hours . how far is she from the end of the trail

It is very important to look at all the information's that are given in the question. Based on those given information's the answer to the question can be easily deduced.
Length of the blue lake trail = 11 3/8 miles
                                            = 91/8 miles
Distance hiked by Gemma per hour = 2 1/2 miles
                                                          = 5/2 miles
Then
Distance hiked by Gemma in 3 hours = (5/2) * 3 miles
                                                             = 15/2 miles
Then
Distance from the end of the trail = (91/8) - (15/2) miles
                                                    = (91 - 60)/8 miles
                                                    = 31/8 miles
                                                    = 3 7/8 miles
So it can be concluded from the above deduction that the distance that is still left for Gemma to cover the trail is 3 7/8 miles. I hope there is nothing complicated in the procedure for you to not understand.