Abbot can do some work in 10 days, Bill can do it in 20 days and Clinton can do it in 40 days. They start working in turns with Abbot starting to work on the first day followed by Bill on the 2nd day and by Clinton on the 3rd day and again by Abbot on the fourth day and so ontill the work is completed fully.find the time to complete the work fully.

17 Days in My opinion.
Consider Total Units as 200
Abbot works : 200/10 = 20units/day
Bill works : 200/20 = 10 units/day
Clinton : 200/40 = 5 units/day

Together they work on each day as Abbot + Bill+ Clinton = 20+10+5 = 35 units/day
Total Time taken to complete the task : 200/35 = 5.714 days

Since each person works seperately for 1 day i.e Bill,Abbot, Clinton working on seperate days ,final solution will be: Total Days working together * total people = 5.714 days * 3 = ~ 17days

Answer = 17days

U can also consider 35/units per 3 days as each works seperately , so = 35/3 = 11.667 units/day
Final Solution = Total units/ units per day = 200/11.667 = ~17days

Answer = 16.5 Days
Solution =
abbot one day work=1/10
bill one day work=1/20
clinton one day work=1/40
then 1/10+1/20+1/40=3 day work
(8+4+2)*5/80=3*5 day
then
left work=1-7/8=1/8
then 1/8-1/10 then=then work left=1/40
then day=15+1
then next daaaay 1/40-1/20 then this is neg
(1/40)/(1/20)=1/2then
Total day 16.5 Days