A centroid printer is a fast-print printer with a speed of 20 pages per minute. A surefire printer is also fast but it's a bit slower with a printing speed of 15 pages per minute. So,
180 pages / (20 pages per minute) - 180 / (15 pages per minute)
= 36 minutes
It would take 36 minutes faster for the centroid printer to print the document than a surefire printer.
