Payton drives 7 3/4
and Jessie drives 6 3/8
to find how much farther Payton drives subtract them
7 3/4 - 6 3/8
find the LCD or least common denominator in the fractions
3/4 = 6/8 so now you have
7 6/8 - 6 3/8
7-6 = 1
6/8 - 3/8 = 3/8
gives you 1 3/8 miles farther