Answer
Please see the work below.
Work Step by Step
We know that
$t=\frac{x}{v_1}$
$t=\frac{100}{9}=11.11s$
$d_2=(v_2)(t)$
We plug in the known values to obtain:
$d_2=(0.80\times 9.0)(11.11)$
$d_2=80m$
Thus, they should give him a head start of 20m.
