Alright, let's solve this math problem step by step. First, we have the number 891. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 45. So, we're going to take the number 891 and add it to itself 45 times.
Step 1: 0 + 891 = 891
Step 2: 891 + 891 = 1782
Step 3: 1782 + 891 = 2673
Step 4: 2673 + 891 = 3564
Step 5: 3564 + 891 = 4455
Step 6: 4455 + 891 = 5346
Step 7: 5346 + 891 = 6237
Step 8: 6237 + 891 = 7128
Step 9: 7128 + 891 = 8019
Step 10: 8019 + 891 = 8910
Step 11: 8910 + 891 = 9801
Step 12: 9801 + 891 = 10692
Step 13: 10692 + 891 = 11583
Step 14: 11583 + 891 = 12474
Step 15: 12474 + 891 = 13365
Step 16: 13365 + 891 = 14256
Step 17: 14256 + 891 = 15147
Step 18: 15147 + 891 = 16038
Step 19: 16038 + 891 = 16929
Step 20: 16929 + 891 = 17820
Step 21: 17820 + 891 = 18711
Step 22: 18711 + 891 = 19602
Step 23: 19602 + 891 = 20493
Step 24: 20493 + 891 = 21384
Step 25: 21384 + 891 = 22275
Step 26: 22275 + 891 = 23166
Step 27: 23166 + 891 = 24057
Step 28: 24057 + 891 = 24948
Step 29: 24948 + 891 = 25839
Step 30: 25839 + 891 = 26730
Step 31: 26730 + 891 = 27621
Step 32: 27621 + 891 = 28512
Step 33: 28512 + 891 = 29403
Step 34: 29403 + 891 = 30294
Step 35: 30294 + 891 = 31185
Step 36: 31185 + 891 = 32076
Step 37: 32076 + 891 = 32967
Step 38: 32967 + 891 = 33858
Step 39: 33858 + 891 = 34749
Step 40: 34749 + 891 = 35640
Step 41: 35640 + 891 = 36531
Step 42: 36531 + 891 = 37422
Step 43: 37422 + 891 = 38313
Step 44: 38313 + 891 = 39204
Step 45: 39204 + 891 = 40095

So, 891*45 = 40095