For history class, Joe spent 2 hours writing a 4-page report on ancient Egypt. This weekend, he needs to write a 12-page report on the Roman Empire.
If he writes at the same rate, how long will it take Joe to write his report?
If Joe spent 2 hours writing a 4-page report, then the rate at which he writes is 2 hours/4 pages = <<2/4=0.5>>0.5 hours per page.
Therefore, it will take Joe 0.5 hours/page x 12 pages = <<0.5*12=6>>6 hours to write his report. Answer: \boxed{6}.