You can
put this solution on YOUR website! Sally can paint a room in 3 hours while it takes Steve 4 hours to paint the
same room. How long would it take them to paint the room if they worked
together?
The LCM of 3 hours and 4 hours is 12 hours. If they worked together for 12
hours Sally would paint 4 rooms while Steve would paint 3 rooms. So together
they can paint 7 rooms in 12 hours, so they could paint 1 room in 7/12 hours
or 35 minutes.