A painter can paint a house in 3 days. When his helper works with him, both men can paint the house in 2 days. How long will it take the helper, working alone, to paint the house?

In one day a painter can do 1/3 of house.

If both of them work together can do 1/2 of work.

In one day helper can d0 1/2-1/3 of work =(3-2)/6 =1/6 of work.

Time taken by the helper to do =6 days.