SOLUTION: Jeff & Kirk can build a 75- ft retaining wall together in 9 hours. Because Jeff has more experience be can build the wall by himself 2 hours quicker than Kirk. How long would it ta

Question 1034843: Jeff & Kirk can build a 75- ft retaining wall together in 9 hours. Because Jeff has more experience be can build the wall by himself 2 hours quicker than Kirk. How long would it take Kirk to the nearest minute to build the wall by himself?
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
Call the time Kirk takes alone, t hours.
Thus Jeff can do it in t-2 hours.
The setup looks like this

Multiply by t(t-2) and get
9(t-2) + 9t = t(t-2)
Now solve for t...
9t - 18 + 9t = t^2 - 2t
t^2 - 20t + 18 = 0
t = 19.0554 hours = 19 hours 3 minutes
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