SOLUTION: I'm having a brain cramp and can't figure out the formula. I can figure it out if they both work together, but the 2 hours is goofing me up. An expert can do a job in 6 hours.

Question 29092: I'm having a brain cramp and can't figure out the formula. I can figure it out if they both work together, but the 2 hours is goofing me up.
An expert can do a job in 6 hours. An helper can do the same job in 7 hours. If the expert works for 2 hours, how long does it take for the helper to finish?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The expert works at a rate of (1/6)job per hour.
The helper finishs (2/7)job in two hours, leaving (5/7)of the job to be done.
EQUATION:
Let x be the number of hours the expert has to work to finish the job.
Then (1/6)x=5/7
x=30/7 hrs. = 4 2/7 hrs= 60min. + (2/7)60 min.= 4 hr. 17 minutes.
Cheers,
stan H.
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