A can complete a task in 12 days. B can complete the task in 18 days....
A can complete a task in 12 days and B can complete the task in 18 days.
In one day, A can do 1/12, in one day B can do 1/18
In two days, they can complete 1/12 + 1/18 = which is 5/36
In 4 days, they can finish 10/36, and so on.
We can have 7 such sets of 2 days each.
So, at the end of 14 days, they would have done 35/36 of task.
On the 15 day A would begin work with 1/36 of the task to finish. He can finish 1/12 in a day. So,
he would take one-third of a day. So, they can finish the whole task in 14.33 days.
Hence, the correct option is (a).