Answer: he increased the distance he hiked each day by 1/3 mile
Step-by-step explanation:
The first day he hiked 1/6 of a mile, the second day he hiked 1/2 of a mile. The amount by which his distance increased between the first and second day is
1/2 - 1/6 = 2/6 = 1/3 mile
the third day he hiked 5/6 of a mile. The amount by which his distance increased between the second and third day is
5/6 - 1/2 = 2/6 = 1/3 mile