SOLUTION: I need help understanding how to solve and write this problem. I also want to understand the concept of it. A roofer can shingle a house in 12 hours. He starts a house with an a

Question 468223: I need help understanding how to solve and write this problem. I also want to understand the concept of it.
A roofer can shingle a house in 12 hours. He starts a house with an apprentice and they work 3 hours until the roofer falls off and is carried away. It takes the apprentice another 12 hours to finish. How long would it take the apprentice working alone to do an entire home?
Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
The roofer can do 1/12 the job in 1 hr.
The apprentice can do the job in x hrs. and can do 1/x of the job in 1 hr.
3(1/12 + 1/x) + 12/x = 1 (job)
(3/12 + 3/x) + 12/x = 1
1/4 + 3/x + 12/x = 1
x+12+48=4x multiply each side by 4x.
3x=60
x=20 hrs time it would take the apprentice working alone to do an entire home.
.
Ed

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