Party A works alone for 6 days and Party B works alone for 5 days. * * * 27% of the total project quantity is completed, which can be converted into 5 days of cooperation between Party A and Party B, and then Party A works alone 1 day.

So the working efficiency of A is 27/40- 1/8*5= 1/20.

So it takes a person1(1/20) = 20 days.