tracy can wallpaper 2 rooms in a new house in 4 hrs. together with her trainee they can wallpaper the 2 rooms in 3 hours. how long would it take the trainee working by herself to do the job?

Question

y2o2 · Answer

let tracy be x and the trainee be y: 
then

$$2 \div (x+y) = 3$$
$$2 \div x = 4$$
therefore ;
$$x+y = (2/3)$$
$$x = 0.5$$

$$y = (1/6)$$
$$2 \div (y) = 2 \div (1/6) = 12$$

The trainee would take 12 hours to finish the job alone.

y2o2 · Answer

I think there's a simpler answer...but i don't know it :)