Group plans d days but k men leave each day, finishes later: initial number of men

The same question, asked 3 times: 25 Jul 2023 S1*, 25 Jul 2023 S4*, 26 Jul 2023 S1. Every wording below, oldest first.

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Question 1
25 Jul 2023 S1
68 $A group of men decided to do a job in 13 days but 9 men left the work after each day. The work, as a result, got completed in 16 days. How many men were initially in the group?$
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Question 2
25 Jul 2023 S4
53 $A group of college students had decided to complete a project in 10 days. As 2 students dropped out every day, the project got completed at the end of the 15th day. The number of students at the beginning of the project was:$
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Question 3
26 Jul 2023 S1
61 $A group of men decided to do a job in 11 days but 16 men left the work after each day. The work, as a result, got completed in 15 days. How many men were there initially in the group?$
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Question 1