Question 1085596
Car 1: {{{D[1]=R[1]*t}}}
Car 2: {{{D[2]=(R[1]+8)*t}}}
So at 9pm, {{{t=9-4=5}}},
{{{D[1]+D[2]=600}}}
{{{R[1]*5+(R[1]+8)*5=600}}}
{{{R[1]+R[1]+8=120}}}
{{{2R[1]=112}}}
{{{R[1]=56}}}{{{mph}}}