Bob can refinish the floor in 6 fewer hours than it takes Alice to refinish the same floor. it takes 4 hours to do it together. How long will it take each of them?

let x - Alice

x - 6 = Bob

x(x-6) / (x + x -6 ) = 4

x^2 - 6x /2x -6 = 4

x^2 - 6x = 8x -24

x^2 - 14x +24 = 0

(x-12) (x -2) = 0

x =12 hours Alice

Bob = 6 hours