Question 930639
Eric and Ryan have been hired to pain the houses in a new development. Working together the men can paint the house in two-thirds the time that it takes eric working alone. Ryan takes six hours to paint a house alone. How long does it take eric to paint a house working alone? 
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It takes Eric E hours, take Ryan R hours (each working alone)
Eric does 1/E per hour, Ryan does 1/R per hour.
R = 6 hours
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 They do (1/E + 1/6) = (E + 6)/6E job/hour together
--> 6E/(E + 6) hours/job together
6E/(E + 6) = (2/3)E
6/(E + 6) = (2/3)
2(E + 6) = 18
E = 3 hours