In order to solve this, you first need to find how long it takes to print 10 copies, and multiply that by 10. To get this, you divide 30 by 3 and 12 by 3 to get that it takes 4 minutes to print 10 copies. Then you multiply 4 by 10 and 10 by 10 to get that it takes 40 minutes to print 100 copies.
