Question 336546
Rate*Time=Distance
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During that {{{1/2}}} hour difference, Train A travel {{{30}}} miles from the station.
Start counting time when Train B passes the station.
Train A's distance from the station is 
{{{Da=60t+30}}}
Train B's distance from the station is,
{{{Db=70t}}}
Find {{{t}}} when {{{Da=Db}}}.
{{{60t+30=70t}}}
{{{10t=30}}}
{{{t=3}}}
It will take Train B three hours to catch up to Train A.