Question 876149
Here's how I would do it:
{{{ d = r*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
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Putting into a formula:
Let {{{ d }}} = distance from the finish line 
after 9 sec
{{{ d = 100 - ( 9*( 9-1 ) ) - 8 }}}
{{{ d = 100 - 72 - 8 }}}
{{{ d = 20 }}} m
where {{{ ( 9*( 9-1 ) ) }}} = rate x time