Men alone and women alone take given days: days for a mixed group

The same question, asked 2 times: CDS 1 2017*, CDS 1 2018. Every wording below, oldest first.

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Question 1
CDS 1 2017
30 $If 5 men can do a piece of work in 10 days and 12 women can do the same work in 15 days, the number of days required to complete the work by 5 men and 6 women is$
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Question 2
CDS 1 2018
25 $A work when done by 10 women is completed in 12 days. The same work can be completed in 8 days when done by 5 men. How many days will it take to complete when 6 women and 3 men are employed to perform the same job?$
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Question 1