If your asking for how long it would take y to complete it
Answer:
If X can finish it in 12 days alone
In four days he can finish 4/12 or 33.33% of the work.
This means y finished 66.66% in four days.
4/x =66.66%
x=6
If they ask how long it would take Y to complete it alone
Answer:
So y would complete this work alone in 6 days
If they are asking for how much work each of them did in the four day
Answer:
Y did 66.66% in the 4 days and X did 33.33%
