Question 152195
This is a shared work problem.
Let the total work be 1.
Worker A can do 1/6 of the total work in one day.
Worker B can do 1/4 of the total work in one day.
Working jointly, they can do 1/6 + 1/4 = 2/12 + 3/12 = 5/12 of the total work.
So it takes them 1/(5/12) = 12/5 days to finish the job.