A takes 6 days less than B to finish a piece of work. If both A and B together can finish the work in 4 days, find the time taken by B to finish the work.
If both A and B together can finish it in 4 days, how many days will B take to finish the work? ⇒x=12 or x = 2 x cannot be less than 6. Therefore, B also can finish the work in 12 days.
