Question 351037
Let x=roofer's time and x+6 the assistants time to do the job.
In an hr roofer can do 1/x of the job and the asst. 1/(x+6) of the job.
1/x + 1/x+6 = 1/4
4(x+6)+4x=x(x+6) multiply each side by 4x(x+6)
4x+24+4x=x^2+6x
x^2-2x-24=0
(x-6)(x+4)=0
x=6 hrs
x+6=12 hrs the assistant working alone.
.
Ed