Answer:
12/11 days
Explanation:
Sam can do a job in 4 days.
So in 1 day , he can do 1/4 of the job.
Lisa can do a job is 6 days.
So in 1 day she can do 1/6 of the job
Tom can do a job in 2 days.
So in 1 day he can do the job in 1/2 days.
Taken together, all three of them can do:
of the job.
=
of the job
= 11/12 of the job in 1 day
As a result the job can be completed by all three of them together in 12/11 days.