Suppose can paint the room in hours,
. . . . . . can paint the room in hours,
. . . . . . can paint the room in hours.
In one hour, can paint of the room.
In one hour, can paint of the room.
In one hour, can paint of the room.
In one hour, and can paint of the room.
Since it takes both of them hours together,
. . in one hour, they can paint of the room: . . [1]
In one hour, and can paint of the room.
Since it takes both of them hours together,
. . in one hour, they can paint of the room: . . [2]
In one hour, and can paint of the room.
Since it take both of them hours,
. . in one hour, they can paint of the room: . . [3]
Subtract [2] from [1]: .
. . . . . . . . . .Add [3]: .
And we have: .
Substitute into [1]: .
Substitute into [3]: .
Punchline: does negative work.
As Dan pointed out, must be using paint remover.
(Their names must be: Curly, Larry and Moe.)