Question 538848
a = airspeed
w = wind speed
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(a+w)*5 hr = 2250 miles
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(a-w)*5 hr = 1750 miles
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Using the distributive property to eliminate the parentheses.
Then solve the system of equations by elimination
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5a + 5w = 2250
5a - 5w = 1750
--------------- add
10a = 4000
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a = 400
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Substitute a = 400 to find 'w'.
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5(400) + 5w = 2250
2000 + 5w = 2250
5w = 250
w = 50
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Check the distances traveled in 5 hr to make sure these answers are right.
(400+50)*5 = 2250 
(400-50)*5 = 1750
Correct.
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Answer:  Airspeed in calm air is 400 mph.  The wind speed is 50 mph.
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Done.