Answer:
Ram takes 20 days to complete a piece of work.
Shyam takes 30 days to complete a piece of work.
Ram completes (1/20) of a piece of work in 1 day.
Shyam completes (1/30) of a piece of work in 1 day.
Together R and S complete (1/20) + (1/30) = (1/12) of a piece of work in 1 day.
(1/12) of a piece of work - 1 day
(12/12) of a piece of work - (12/12)/(1/12) = 12 days.
R and S take 12 days to complete a piece of work when they work together
