X and Y together can complete a piece of work in 4 days. If X alone can complete the same work in 12 days.

that work?
plz Do it step-by-step.

If your asking for how long it would take y to complete it

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

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

Y did 66.66% in the 4 days and X did 33.33%

Iam not sure , but probably 750 or 7.5