Sally can paint a room in 4 hours while it takes steve 9 hours to paint the same room. how long would it take them to paint the room if they worked together

Sally  ⇒
4 hours = 1 room
1 hour = 1/4 of the room

Steve ⇒
9 hours = 1 room
1 hour = 1/9 of the room

Sally + Steve ⇒
1 hour = 1/4 + 1/9 = 9/36 + 4/36 = 13/36

Number of hours needed ⇒
1 ÷ 13/36 = 1 x 36/13 = 36/13 = 2 10/13 hours

They need 2 10/13 hours.