<PRE><B>Question 707434</B>
Let x = time it takes for Roger to do the job alone


So x+9 = time it takes for Dale to do the job alone


1/x + 1/(x+9) = 1/6


x+9/(x(x+9)) + x/(x(x+9)) = 1/6


(x+9 + x)/(x(x+9)) = 1/6


(2x+9)/(x(x+9)) = 1/6


6(2x+9) = 1*x(x+9)


12x + 54 = x^2 + 9x


0 = x^2 + 9x - 12x - 54


x^2 - 3x - 54 = 0


(x - 9)(x + 6) = 0


x-9 = 0 or x+6 = 0


x = 9 or x = -6


Ignore the negative answer.


So Roger can do the job in 9 hours if he does it alone


Dale can do the job in 18 hours if he does it alone
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