If 6 machines takes 12 days
to complete the same work in 8 days we nedd12/8 x 6 = 9 machines
So 3 machines are needed additionally.
So B is the answer.
Hey Buddy, this is a simple question. Please go through the basics of every topic. I think then only u can understand most of the questions posted here in this forum
Averages Accelerated:Guide to solve Averages Quickly(with 10 practice problems)