Question 402056
Hello, 
Let's have x represent the number of hours it will take 2 people working together to complete the job. Here's the equation we can set up:
1/7(x)+1/6(x)=1 (whole job)
Multiply this by 42 to get:
6x+7x=42
Combine like terms and divide by 13 to get:
x=42/13 or 3 3/13 hours working togeter to clean the attic. 
Make sense?
RJ
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