A man can do the job in 8 days after 3 days of working a new guy help him and it takes 3 more days to finish the job together. how long will it take the new guy to finish the job alone?

Answer 1

After 3 days, there is still 5/8 job left to do.

(5/8)/3 = 1/8 + 1/x
x = 12

Check:
In 3 days, the man can do 3/8 of the work
The helper can do 3/12 = 1/4 of the work

3/8 + 1/4 = 5/8, the amount of the work left to do.