From the information given, it can be concluded that:
Sam can do 1/4 of the job in one day.
Lisa can do 1/6 of the job in one day.
and Tom can do 1/2 of the job in one day.

In one day, if they work together they can complete 11/12(1/4+1/6+1/2) of the job.  To finish the other 1/12 of the job, it will take 1/11 of the second day, because 1/11 times 11/12 is equal to the other 1/12 necessary to complete the job. 

If they worked together, it would take 1 1/11 days.

Check: (1/4+1/6+1/2)*(1 1/11) = 1 <p><marquee behavior="alternate">Solved By: NtNk</marquee>