If Sally paints one room per six hours, she paints 1/6 of the room every hour. Similarly, Steve paints 1/9 of the room every hour. Therefore, together, they paint 1/6+1/9=5/18 of the room every hour. Therefore, it takes the 18/5 of an hour to paint the whole room, since 18/5*5/18=1, so 18/5 of an hour at 5/18 of the room per hour is one room.
