Ana is using a photocopier to make 315 copies of a poster. It takes 3 minutes to print the first 63 posters. If the photocopier continues to print at the same rate, how many more minutes will it take to complete the job?
If it takes 3 minutes to print 63 posters, then Ana can print 63/3 = <<63/3=21>>21 posters per minute.
To make 315 copies, Ana will need an additional 315 - 63 = <<315-63=252>>252 copies.
At a rate of 21 posters per minute, it will take an additional 252/21 = <<252/21=12>>12 minutes to complete the job. Answer: \boxed{12}.