212x37十172x56=(172+40)x37十172x56=172×(37+56)+40×37=172×(100-7)+1480=17200-172×7+1480=17200-1204+1480=17200+276=17476
212X37+172X56=212X(40-3)+172X(60-4)=8480-636+10320-688=18800-1324=17476