Assuming that the total amount of the whole project is 1, it will take X hours for Party A to complete112 in one hour and Party B to complete118 in one hour. List:

x( 1/ 12+ 1/ 18)/2 = 1

Solution x= 14.4, but after Party A and Party B work for 7 hours each, there is still 1/36 left in this project, so Party A will work next, and Party A will work112, 1/36 every hour, which will cost Party A 65438+.