X does a work in 6 days, while Y does it in 12 days. If they work alternatively and X begins, in how many days will the work be finished?

7 5 8 6

8

X = 6 days, Y = 12 days, ⇒ They work alternatively, starting with X,  1st day = 2  2nd day = 1 Every 2 days = 3 units So,in 8 days, 12 units of work will be completed. Therefore, work will be completed in 8 days.