Question 14242
If Alan do the entire research paper 6 hours, then he can do 1/6 of the job in 1 hour.
If Alan & Steve together can do the research paper in 4 hours, then they can do 1/4 of the job in 1 hour.

Find out how much of the job Steve can do by himself in 1 hour.

Steve+Alan - Alan = Steve.
{{{1/4 - 1/6 = 1/12}}}  This means that Steve can do 1/12 of the job in 1 hour.

So it will take Steve 12 hours to do the entire job.