OK, let's crack this. We're given 671 and our task is to multiply it by 43. Essentially, we'll be adding 671 to itself 43 times.
Step 1: 0 + 671 = 671
Step 2: 671 + 671 = 1342
Step 3: 1342 + 671 = 2013
Step 4: 2013 + 671 = 2684
Step 5: 2684 + 671 = 3355
Step 6: 3355 + 671 = 4026
Step 7: 4026 + 671 = 4697
Step 8: 4697 + 671 = 5368
Step 9: 5368 + 671 = 6039
Step 10: 6039 + 671 = 6710
Step 11: 6710 + 671 = 7381
Step 12: 7381 + 671 = 8052
Step 13: 8052 + 671 = 8723
Step 14: 8723 + 671 = 9394
Step 15: 9394 + 671 = 10065
Step 16: 10065 + 671 = 10736
Step 17: 10736 + 671 = 11407
Step 18: 11407 + 671 = 12078
Step 19: 12078 + 671 = 12749
Step 20: 12749 + 671 = 13420
Step 21: 13420 + 671 = 14091
Step 22: 14091 + 671 = 14762
Step 23: 14762 + 671 = 15433
Step 24: 15433 + 671 = 16104
Step 25: 16104 + 671 = 16775
Step 26: 16775 + 671 = 17446
Step 27: 17446 + 671 = 18117
Step 28: 18117 + 671 = 18788
Step 29: 18788 + 671 = 19459
Step 30: 19459 + 671 = 20130
Step 31: 20130 + 671 = 20801
Step 32: 20801 + 671 = 21472
Step 33: 21472 + 671 = 22143
Step 34: 22143 + 671 = 22814
Step 35: 22814 + 671 = 23485
Step 36: 23485 + 671 = 24156
Step 37: 24156 + 671 = 24827
Step 38: 24827 + 671 = 25498
Step 39: 25498 + 671 = 26169
Step 40: 26169 + 671 = 26840
Step 41: 26840 + 671 = 27511
Step 42: 27511 + 671 = 28182
Step 43: 28182 + 671 = 28853

So, 671*43 = 28853