Using the formula:
d = r x t
9 sec after the race started is 8 sec after
he started sprinting
d=9.8
d=72
So, he has gone 8 + 72= 80 m
That means he is 100 - 80 = 20 m from the finish line.
Putting into a formula:
Let,
d = distance from the finish line after 9 sec
d=100-(9(9-1)) - 8
d= 20 m