OK, let's work through this together. We're starting with 821 and we're going to multiply it by 45, which means we add 821 to itself 45 times.
Step 1: 0 + 821 = 821
Step 2: 821 + 821 = 1642
Step 3: 1642 + 821 = 2463
Step 4: 2463 + 821 = 3284
Step 5: 3284 + 821 = 4105
Step 6: 4105 + 821 = 4926
Step 7: 4926 + 821 = 5747
Step 8: 5747 + 821 = 6568
Step 9: 6568 + 821 = 7389
Step 10: 7389 + 821 = 8210
Step 11: 8210 + 821 = 9031
Step 12: 9031 + 821 = 9852
Step 13: 9852 + 821 = 10673
Step 14: 10673 + 821 = 11494
Step 15: 11494 + 821 = 12315
Step 16: 12315 + 821 = 13136
Step 17: 13136 + 821 = 13957
Step 18: 13957 + 821 = 14778
Step 19: 14778 + 821 = 15599
Step 20: 15599 + 821 = 16420
Step 21: 16420 + 821 = 17241
Step 22: 17241 + 821 = 18062
Step 23: 18062 + 821 = 18883
Step 24: 18883 + 821 = 19704
Step 25: 19704 + 821 = 20525
Step 26: 20525 + 821 = 21346
Step 27: 21346 + 821 = 22167
Step 28: 22167 + 821 = 22988
Step 29: 22988 + 821 = 23809
Step 30: 23809 + 821 = 24630
Step 31: 24630 + 821 = 25451
Step 32: 25451 + 821 = 26272
Step 33: 26272 + 821 = 27093
Step 34: 27093 + 821 = 27914
Step 35: 27914 + 821 = 28735
Step 36: 28735 + 821 = 29556
Step 37: 29556 + 821 = 30377
Step 38: 30377 + 821 = 31198
Step 39: 31198 + 821 = 32019
Step 40: 32019 + 821 = 32840
Step 41: 32840 + 821 = 33661
Step 42: 33661 + 821 = 34482
Step 43: 34482 + 821 = 35303
Step 44: 35303 + 821 = 36124
Step 45: 36124 + 821 = 36945

So, 821*45 = 36945