Convert each fraction so they both have a common denominator by finding the lowest common denominator.
The lowest common denominator of 6 and 8 is 24. 8 goes into 24 3 times and 6 goes into 24 4 times.
now convert the fractions: 7/8 = 21/24
and 5/6 = 20/24
Now subtract:
21/24 - 20/24 = 1/24
Pam walks 1/24 of a mile more.
