Sure thing, let's get straight to it. We start with 671 and we're going to multiply it by 87, which means adding 671 to itself 87 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
Step 44: 28853 + 671 = 29524
Step 45: 29524 + 671 = 30195
Step 46: 30195 + 671 = 30866
Step 47: 30866 + 671 = 31537
Step 48: 31537 + 671 = 32208
Step 49: 32208 + 671 = 32879
Step 50: 32879 + 671 = 33550
Step 51: 33550 + 671 = 34221
Step 52: 34221 + 671 = 34892
Step 53: 34892 + 671 = 35563
Step 54: 35563 + 671 = 36234
Step 55: 36234 + 671 = 36905
Step 56: 36905 + 671 = 37576
Step 57: 37576 + 671 = 38247
Step 58: 38247 + 671 = 38918
Step 59: 38918 + 671 = 39589
Step 60: 39589 + 671 = 40260
Step 61: 40260 + 671 = 40931
Step 62: 40931 + 671 = 41602
Step 63: 41602 + 671 = 42273
Step 64: 42273 + 671 = 42944
Step 65: 42944 + 671 = 43615
Step 66: 43615 + 671 = 44286
Step 67: 44286 + 671 = 44957
Step 68: 44957 + 671 = 45628
Step 69: 45628 + 671 = 46299
Step 70: 46299 + 671 = 46970
Step 71: 46970 + 671 = 47641
Step 72: 47641 + 671 = 48312
Step 73: 48312 + 671 = 48983
Step 74: 48983 + 671 = 49654
Step 75: 49654 + 671 = 50325
Step 76: 50325 + 671 = 50996
Step 77: 50996 + 671 = 51667
Step 78: 51667 + 671 = 52338
Step 79: 52338 + 671 = 53009
Step 80: 53009 + 671 = 53680
Step 81: 53680 + 671 = 54351
Step 82: 54351 + 671 = 55022
Step 83: 55022 + 671 = 55693
Step 84: 55693 + 671 = 56364
Step 85: 56364 + 671 = 57035
Step 86: 57035 + 671 = 57706
Step 87: 57706 + 671 = 58377

So, 671*87 = 58377