The task is to generate the correct answer for a given math problem.

Q: Problem: if 1 / ( x + 4 ) + 1 / ( x - 4 ) = 1 / ( x - 4 ) , what is the value of x ?

A: 4
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Q: Problem: 9 . on level farmland , two runners leave at the same time from the intersection of two country roads . one runner jogs due north at a constant rate of 8 miles per hour while the second runner jogs due east at a constant rate that is 8 miles per hour faster than the first runner ' s rate . how far apart , to the nearest mile , will they be after 1 / 2 hour ?

A: 
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Q: Problem: a man rows his boat 120 km downstream and 92 km upstream , taking 4 hours each time . find the speed of the stream ?

A:
4 kmph
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