Well,
In 1 hour, Tim painted 1/6th of the room.
In 1 hour, Ben painted 1/4th of the room
1/6+1/4
Make them both have a common denominator: 1/6=2/12 and 1/4=3/12
In 1 hour, they can paint 5/12th of the room.
Like in the beginning, I flipped the numbers 6 and 4 to 1/6 and 1/4 to get how much painting they did in 1 hour.
If going to flip the fraction 5/12 to 12/5 to get how much painting they can do in all. Make sense?
12/5 is 2.4, which is 2 hours and 24 minutes.
Hope I helped!