Examine this presentation and compare with your example, and try to solve.
Note carefully that your example uses equal distance in both directions.
travel rates equal times different distances, involve wind
Did it help? The channel has also another example of travel rates which may yet be helpful.
Some help with the data table, based on travel rates rule RT=D, and implied variable assignments:
rate time distance
WITH WIND r+w 4 2400
AGAINST WIND r-w 2400