<PRE><B>Question 1175653</B>
&lt;br&gt;
Informally....&lt;br&gt;
In the 3 hours before the Air Force plane starts, the jet flies a total of 168*3 = 504 miles.&lt;br&gt;
When both planes are flying, the Air Force plane catches up to the jet at a rate of (240-168)=72 mph.&lt;br&gt;
The amount of time required to make up 504 miles at 72mph is 504/72 = 7 hours.&lt;br&gt;
ANSWER: 7 hours&lt;br&gt;
With formal algebra, you end up doing virtually the same calculations:&lt;br&gt;
x = number of hours Air Force plane flies
x+3 = hours the jet flies&lt;br&gt;
The distance the Air Force plane flies in x hours at 240mph is the same as the distance the jet flies in (x+3) hours at 168mph:&lt;br&gt;
{{{240x = 168(x+3)}}}
{{{240x = 168x+504}}}
{{{72x = 504}}}
{{{x = 504/72 = 7}}}&lt;br&gt;
ANSWER: (same as before, of course!): 7 hours&lt;br&gt;
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