Answer: 3/8 of a mile
Step-by-step explanation: To make this a bit more understandable, 7/8 cannot have a denominator of 2 since the numerator is 7, so what we do is make 1/2 of a mile have a denominator of 8. So we turn 1/2 to 4/8 to make the fractions more easier to use by multiplying 1/2 by 4.
1/2 X 4 = 4/8
So, Dawn rode 4/8 of a mile and she needs to get to a point where it is 7/8 of a mile away from her starting point. When you subtract fractions, you do not have to worry about the denominator, just the numerator.
7/8 - 4/8 = 3/8
Therefore, dawn must hike 3/8 of a mile more to reach her goal. :)