Question 1073639
You are one mile from the railroad station, and your train is due to leave in ten minutes.
Let walking time be "x" min; running time be "10-x" min
You have been walking at a steady rate of 3 mph, and you can run at 8 mph if you have to.
For how many more minutes can you continue walking, until it becomes necessary for you
to run the rest of the way to the station? 
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Equation:
dist + dist = 1 mile
(3/60)x + (8/60)(10-x) = 1 mile
3x + 80-8x = 60
-5x = -20
x = 4 min (walking time)
10-x = 6 min (running time)
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Cheers,
Stan H.
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