Sure thing, let's get straight to it. We start with 945 and we're going to multiply it by 90, which means adding 945 to itself 90 times.
Step 1: 0 + 945 = 945
Step 2: 945 + 945 = 1890
Step 3: 1890 + 945 = 2835
Step 4: 2835 + 945 = 3780
Step 5: 3780 + 945 = 4725
Step 6: 4725 + 945 = 5670
Step 7: 5670 + 945 = 6615
Step 8: 6615 + 945 = 7560
Step 9: 7560 + 945 = 8505
Step 10: 8505 + 945 = 9450
Step 11: 9450 + 945 = 10395
Step 12: 10395 + 945 = 11340
Step 13: 11340 + 945 = 12285
Step 14: 12285 + 945 = 13230
Step 15: 13230 + 945 = 14175
Step 16: 14175 + 945 = 15120
Step 17: 15120 + 945 = 16065
Step 18: 16065 + 945 = 17010
Step 19: 17010 + 945 = 17955
Step 20: 17955 + 945 = 18900
Step 21: 18900 + 945 = 19845
Step 22: 19845 + 945 = 20790
Step 23: 20790 + 945 = 21735
Step 24: 21735 + 945 = 22680
Step 25: 22680 + 945 = 23625
Step 26: 23625 + 945 = 24570
Step 27: 24570 + 945 = 25515
Step 28: 25515 + 945 = 26460
Step 29: 26460 + 945 = 27405
Step 30: 27405 + 945 = 28350
Step 31: 28350 + 945 = 29295
Step 32: 29295 + 945 = 30240
Step 33: 30240 + 945 = 31185
Step 34: 31185 + 945 = 32130
Step 35: 32130 + 945 = 33075
Step 36: 33075 + 945 = 34020
Step 37: 34020 + 945 = 34965
Step 38: 34965 + 945 = 35910
Step 39: 35910 + 945 = 36855
Step 40: 36855 + 945 = 37800
Step 41: 37800 + 945 = 38745
Step 42: 38745 + 945 = 39690
Step 43: 39690 + 945 = 40635
Step 44: 40635 + 945 = 41580
Step 45: 41580 + 945 = 42525
Step 46: 42525 + 945 = 43470
Step 47: 43470 + 945 = 44415
Step 48: 44415 + 945 = 45360
Step 49: 45360 + 945 = 46305
Step 50: 46305 + 945 = 47250
Step 51: 47250 + 945 = 48195
Step 52: 48195 + 945 = 49140
Step 53: 49140 + 945 = 50085
Step 54: 50085 + 945 = 51030
Step 55: 51030 + 945 = 51975
Step 56: 51975 + 945 = 52920
Step 57: 52920 + 945 = 53865
Step 58: 53865 + 945 = 54810
Step 59: 54810 + 945 = 55755
Step 60: 55755 + 945 = 56700
Step 61: 56700 + 945 = 57645
Step 62: 57645 + 945 = 58590
Step 63: 58590 + 945 = 59535
Step 64: 59535 + 945 = 60480
Step 65: 60480 + 945 = 61425
Step 66: 61425 + 945 = 62370
Step 67: 62370 + 945 = 63315
Step 68: 63315 + 945 = 64260
Step 69: 64260 + 945 = 65205
Step 70: 65205 + 945 = 66150
Step 71: 66150 + 945 = 67095
Step 72: 67095 + 945 = 68040
Step 73: 68040 + 945 = 68985
Step 74: 68985 + 945 = 69930
Step 75: 69930 + 945 = 70875
Step 76: 70875 + 945 = 71820
Step 77: 71820 + 945 = 72765
Step 78: 72765 + 945 = 73710
Step 79: 73710 + 945 = 74655
Step 80: 74655 + 945 = 75600
Step 81: 75600 + 945 = 76545
Step 82: 76545 + 945 = 77490
Step 83: 77490 + 945 = 78435
Step 84: 78435 + 945 = 79380
Step 85: 79380 + 945 = 80325
Step 86: 80325 + 945 = 81270
Step 87: 81270 + 945 = 82215
Step 88: 82215 + 945 = 83160
Step 89: 83160 + 945 = 84105
Step 90: 84105 + 945 = 85050

So, 945*90 = 85050