Question 308472
Colleen can paint a house in 2 hours less than james. Working together they can paint the house in 10 hours. How long would it take james to pain the house by himself?

let james take x hours to paint the house.
He will paint 1/x of the house in 1 hour.
.
.
Colleen takes x-2 hours to do the same job
she will paint 1/ x-2 of the job in 1 hour
..
They both can do the same job in 10 hours
they do 1/10 of the job in 1 hour
.
1/x + 1/ x-2 = 1/10

add the fractions: LCM = x(x-2)
x-2 + x / x(x-2) = 1/10
2x-2 = x(x-2) /10
10(2x-2) = x(x-2)
20x-40= x^2-2x

x^2-22x+40=0
x^2 -20x-2x+40=0
x(x-20)-2(x-20)=0
(x-20)(x-2)=0
x= 20 OR 2 hours
So James can paint the house alone in 20 hours