Let's get this math done. We have 673 and we're going to multiply it by 90. This is the same as taking 673 and adding it to itself 90 times.
Step 1: 0 + 673 = 673
Step 2: 673 + 673 = 1346
Step 3: 1346 + 673 = 2019
Step 4: 2019 + 673 = 2692
Step 5: 2692 + 673 = 3365
Step 6: 3365 + 673 = 4038
Step 7: 4038 + 673 = 4711
Step 8: 4711 + 673 = 5384
Step 9: 5384 + 673 = 6057
Step 10: 6057 + 673 = 6730
Step 11: 6730 + 673 = 7403
Step 12: 7403 + 673 = 8076
Step 13: 8076 + 673 = 8749
Step 14: 8749 + 673 = 9422
Step 15: 9422 + 673 = 10095
Step 16: 10095 + 673 = 10768
Step 17: 10768 + 673 = 11441
Step 18: 11441 + 673 = 12114
Step 19: 12114 + 673 = 12787
Step 20: 12787 + 673 = 13460
Step 21: 13460 + 673 = 14133
Step 22: 14133 + 673 = 14806
Step 23: 14806 + 673 = 15479
Step 24: 15479 + 673 = 16152
Step 25: 16152 + 673 = 16825
Step 26: 16825 + 673 = 17498
Step 27: 17498 + 673 = 18171
Step 28: 18171 + 673 = 18844
Step 29: 18844 + 673 = 19517
Step 30: 19517 + 673 = 20190
Step 31: 20190 + 673 = 20863
Step 32: 20863 + 673 = 21536
Step 33: 21536 + 673 = 22209
Step 34: 22209 + 673 = 22882
Step 35: 22882 + 673 = 23555
Step 36: 23555 + 673 = 24228
Step 37: 24228 + 673 = 24901
Step 38: 24901 + 673 = 25574
Step 39: 25574 + 673 = 26247
Step 40: 26247 + 673 = 26920
Step 41: 26920 + 673 = 27593
Step 42: 27593 + 673 = 28266
Step 43: 28266 + 673 = 28939
Step 44: 28939 + 673 = 29612
Step 45: 29612 + 673 = 30285
Step 46: 30285 + 673 = 30958
Step 47: 30958 + 673 = 31631
Step 48: 31631 + 673 = 32304
Step 49: 32304 + 673 = 32977
Step 50: 32977 + 673 = 33650
Step 51: 33650 + 673 = 34323
Step 52: 34323 + 673 = 34996
Step 53: 34996 + 673 = 35669
Step 54: 35669 + 673 = 36342
Step 55: 36342 + 673 = 37015
Step 56: 37015 + 673 = 37688
Step 57: 37688 + 673 = 38361
Step 58: 38361 + 673 = 39034
Step 59: 39034 + 673 = 39707
Step 60: 39707 + 673 = 40380
Step 61: 40380 + 673 = 41053
Step 62: 41053 + 673 = 41726
Step 63: 41726 + 673 = 42399
Step 64: 42399 + 673 = 43072
Step 65: 43072 + 673 = 43745
Step 66: 43745 + 673 = 44418
Step 67: 44418 + 673 = 45091
Step 68: 45091 + 673 = 45764
Step 69: 45764 + 673 = 46437
Step 70: 46437 + 673 = 47110
Step 71: 47110 + 673 = 47783
Step 72: 47783 + 673 = 48456
Step 73: 48456 + 673 = 49129
Step 74: 49129 + 673 = 49802
Step 75: 49802 + 673 = 50475
Step 76: 50475 + 673 = 51148
Step 77: 51148 + 673 = 51821
Step 78: 51821 + 673 = 52494
Step 79: 52494 + 673 = 53167
Step 80: 53167 + 673 = 53840
Step 81: 53840 + 673 = 54513
Step 82: 54513 + 673 = 55186
Step 83: 55186 + 673 = 55859
Step 84: 55859 + 673 = 56532
Step 85: 56532 + 673 = 57205
Step 86: 57205 + 673 = 57878
Step 87: 57878 + 673 = 58551
Step 88: 58551 + 673 = 59224
Step 89: 59224 + 673 = 59897
Step 90: 59897 + 673 = 60570

So, 673*90 = 60570