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Algebra help

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2 Answers

let x be the speed of the current:
 
16 = (9 - x)t
 
t= 16/(9 - x)
 
substitute t into equation below:
 
15 = (9 + x)(9- t)   ----> -9x2 -x + 450 use quadratic formula ---> [1 ± √[1 - 4*(-9)*450]]/2*(-9)
 
so x ≈ 7.016miles/hour
 
 
Hello again, Erica -- in still water, we could travel 81 miles in 9hr ... current is serious ...
8mph current takes 16hr up ... 7mph current takes 8hr up and 15mi/16mph ~1hr back ...
current is about 7mph  ... Best wishes, ma'am :)

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