Question 326912
Rate*Time=Distance
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.
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{{{Ra=72}}}kph
{{{Rb=78}}}kph
Car A,
Convert from minutes to hrs to be consistent with speed. 
{{{20}}} minutes={{{1/3}}} hr
1.{{{72*(t+1/3)=D}}}
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Car B,
{{{78*t=D}}}
2.{{{t=D/78}}}
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Substitute eq. 2 into eq. 1,
{{{72(D/78+1/3)=D}}}
{{{(72/78)D+26=D}}}
{{{D(1-12/13)=26}}}
{{{D=26/(1/13)}}}
{{{D=26*13}}}
{{{D=338}}}km