Question 1129892
You can think of this as one of them 
traveling at the sum of their speeds for
the entire distance while the other one
is standing still
Let {{{ s }}} = the speed of the bike
in mi/hr
{{{ s + 37.8 }}} = the speed of the car
in mi/hr
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{{{ 578 = ( s + s + 37.8 )*8.5 }}}
{{{ 578 = ( 2s + 37.8 )*8.5 }}}
{{{ 2s + 37.8 = 68 }}}
{{{ 2s = 30.2 }}}
{{{ s = 15.1 }}}
and
{{{ s + 37.8 = 52.9 }}}
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The bike's speed was 15.1 mi/hr
The car's speed was 52.9 mi/hr
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check:
{{{ d[1] = 15.1*8.5 }}}
{{{ d[1] = 128.35 }}}
and
{{{ d[2] = 52.9*8.5 }}}
{{{ d[2] = 449.65 }}}
and
{{{ d[1] + d[2] = 128.35 + 449.65 }}}
{{{ d[1] + d[2] = 578 }}}
OK