Solution:
                    If the machine produce 18 copies every 10 seconds, then
                   18/10 is the number of copies in a second (18/10 = 1.8) 
                   the machine produce 1.8 copies in a second

                    1 hour = 60 minutes; 1 minute = 60 seconds;  then  1 hour = 3600 seconds

                    the machine produce 1.8(3600) copies in an hour               { 1.8(3600) = 6480  }

                    the machine produce 6480 copies in an hour