A large concrete mixing machine can mix a certain amount of concede in 12 hours, while a smallet one can mix the same amount in 20 hours, Mixing simultaneously, how long would it cake both machines to the same
amount of concrete?

One month, a music site observed that 60% of the people who downloaded songs from its site downloaded q sam's latest single. the equation below represents this information, where x represents the total number of people who ddownloaded songs from the site that month: x = 0.6x + 384 how many people who downloaded songs from the site that month downloaded q sam's latest single?