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Was solved many years ago at this forum under this link
https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Rate-of-work-word-problems.faq.question.653878.html
https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Rate-of-work-word-problems.faq.question.653878.html
Alternative to that algebraic solutions is THIS mental solution below:
When they will complete the job, Andrew will complete 5/6 of the job, while Bailey will complete 1/6 of the job.
Thus Bailey makes 1/6 of the job in 9 days.
Hence, Bailey can make the entire job in 6*9 - 54 days working alone.
It implies that Andrew can complete the job in 54/5 = 10 days, working alone.