IF I RAN 3/8 OF A MILE HOW MUCH FURTHER WOULD I HAVE TO RUN TO MAKE A MILE

Answer 1

3/8 + 5/8 = 1

so, you still have 5/8 to go.

and, believe it or not, "further" and "farther" are not interchangeable.

Answer 2

8/8 - 3/8 = ?