Answer:
Jill's best friend jumped 8/21 feet further than Jill.
Explanation:
we have that
Jill jumped 6 1/3 feet
Jill best friend jumped 6 5/7 feet
To find out how much farther did Jill's best friend jumped, subtract the length that Jill jumped from the length that Jill best friend jumped

but first convert mixed number to improper fraction


substitute the values

therefore
Jill's best friend jumped 8/21 feet further than Jill.