Question 1099111
So let the time it takes the passenger train be {{{t}}}. 
Then the freight train time is {{{t+5}}}.
{{{D[p]=63t}}}
{{{D[f]=42(t+5)}}}
But,
{{{D[p]=D[f]}}}
{{{63t=42t+210}}}
{{{21t=210}}}
{{{t=10}}}{{{hr}}}
So then,
{{{D=63(10)}}}
{{{D=630}}}{{{km}}}