684*245-675*246=684*245-675*(245+1)=684*245-675*245-675=245*(684-675)-675=
=245*9-675=2205-675=1530
684 х245 =167580
675х246=166050
167580-166050=1530
684*245-675*246=684*245-675*(245+1)=684*245-675*245-675=245*(684-675)-675=
=245*9-675=2205-675=1530
684 х245 =167580
675х246=166050
167580-166050=1530