A contractor can complete a certain piece of work in 9 days. He employed a certain number of men, but 6 of them are absent from the very first day, the rest could finish the work in 15 days. How many men were originally employed?

The correct answer is: 15 workers

Let’s say that the total work can be represented as W and let’s say the number of workers who completes the work in 9 days is x. It is given that 6 workers left on the very first day and the rest could finish the work in 15 days or we can say x - 6 workers can finish the work in 15 days.
Step 1 of 2:
Work done by x workers in 9 days = W
Work done by x workers in 1 day = 
Work done by 1 worker in 1 day = 
Step 2 of 2:
Work done by x-6 workers in 1 day = 
Work done by x-6 workers in 15 days = 
Also, Work done by x - 6 workers in 15 days = W
So,  = W
15x - 90 = 9x
6x = 90
x = 15 workers
Final Answer:
Hence, 15 men were originally employed