Let's roll up our sleeves and solve this. We have 843 and we're going to multiply it by 143, essentially adding 843 to itself 143 times.
Step 1: 0 + 843 = 843
Step 2: 843 + 843 = 1686
Step 3: 1686 + 843 = 2529
Step 4: 2529 + 843 = 3372
Step 5: 3372 + 843 = 4215
Step 6: 4215 + 843 = 5058
Step 7: 5058 + 843 = 5901
Step 8: 5901 + 843 = 6744
Step 9: 6744 + 843 = 7587
Step 10: 7587 + 843 = 8430
Step 11: 8430 + 843 = 9273
Step 12: 9273 + 843 = 10116
Step 13: 10116 + 843 = 10959
Step 14: 10959 + 843 = 11802
Step 15: 11802 + 843 = 12645
Step 16: 12645 + 843 = 13488
Step 17: 13488 + 843 = 14331
Step 18: 14331 + 843 = 15174
Step 19: 15174 + 843 = 16017
Step 20: 16017 + 843 = 16860
Step 21: 16860 + 843 = 17703
Step 22: 17703 + 843 = 18546
Step 23: 18546 + 843 = 19389
Step 24: 19389 + 843 = 20232
Step 25: 20232 + 843 = 21075
Step 26: 21075 + 843 = 21918
Step 27: 21918 + 843 = 22761
Step 28: 22761 + 843 = 23604
Step 29: 23604 + 843 = 24447
Step 30: 24447 + 843 = 25290
Step 31: 25290 + 843 = 26133
Step 32: 26133 + 843 = 26976
Step 33: 26976 + 843 = 27819
Step 34: 27819 + 843 = 28662
Step 35: 28662 + 843 = 29505
Step 36: 29505 + 843 = 30348
Step 37: 30348 + 843 = 31191
Step 38: 31191 + 843 = 32034
Step 39: 32034 + 843 = 32877
Step 40: 32877 + 843 = 33720
Step 41: 33720 + 843 = 34563
Step 42: 34563 + 843 = 35406
Step 43: 35406 + 843 = 36249
Step 44: 36249 + 843 = 37092
Step 45: 37092 + 843 = 37935
Step 46: 37935 + 843 = 38778
Step 47: 38778 + 843 = 39621
Step 48: 39621 + 843 = 40464
Step 49: 40464 + 843 = 41307
Step 50: 41307 + 843 = 42150
Step 51: 42150 + 843 = 42993
Step 52: 42993 + 843 = 43836
Step 53: 43836 + 843 = 44679
Step 54: 44679 + 843 = 45522
Step 55: 45522 + 843 = 46365
Step 56: 46365 + 843 = 47208
Step 57: 47208 + 843 = 48051
Step 58: 48051 + 843 = 48894
Step 59: 48894 + 843 = 49737
Step 60: 49737 + 843 = 50580
Step 61: 50580 + 843 = 51423
Step 62: 51423 + 843 = 52266
Step 63: 52266 + 843 = 53109
Step 64: 53109 + 843 = 53952
Step 65: 53952 + 843 = 54795
Step 66: 54795 + 843 = 55638
Step 67: 55638 + 843 = 56481
Step 68: 56481 + 843 = 57324
Step 69: 57324 + 843 = 58167
Step 70: 58167 + 843 = 59010
Step 71: 59010 + 843 = 59853
Step 72: 59853 + 843 = 60696
Step 73: 60696 + 843 = 61539
Step 74: 61539 + 843 = 62382
Step 75: 62382 + 843 = 63225
Step 76: 63225 + 843 = 64068
Step 77: 64068 + 843 = 64911
Step 78: 64911 + 843 = 65754
Step 79: 65754 + 843 = 66597
Step 80: 66597 + 843 = 67440
Step 81: 67440 + 843 = 68283
Step 82: 68283 + 843 = 69126
Step 83: 69126 + 843 = 69969
Step 84: 69969 + 843 = 70812
Step 85: 70812 + 843 = 71655
Step 86: 71655 + 843 = 72498
Step 87: 72498 + 843 = 73341
Step 88: 73341 + 843 = 74184
Step 89: 74184 + 843 = 75027
Step 90: 75027 + 843 = 75870
Step 91: 75870 + 843 = 76713
Step 92: 76713 + 843 = 77556
Step 93: 77556 + 843 = 78399
Step 94: 78399 + 843 = 79242
Step 95: 79242 + 843 = 80085
Step 96: 80085 + 843 = 80928
Step 97: 80928 + 843 = 81771
Step 98: 81771 + 843 = 82614
Step 99: 82614 + 843 = 83457
Step 100: 83457 + 843 = 84300
Step 101: 84300 + 843 = 85143
Step 102: 85143 + 843 = 85986
Step 103: 85986 + 843 = 86829
Step 104: 86829 + 843 = 87672
Step 105: 87672 + 843 = 88515
Step 106: 88515 + 843 = 89358
Step 107: 89358 + 843 = 90201
Step 108: 90201 + 843 = 91044
Step 109: 91044 + 843 = 91887
Step 110: 91887 + 843 = 92730
Step 111: 92730 + 843 = 93573
Step 112: 93573 + 843 = 94416
Step 113: 94416 + 843 = 95259
Step 114: 95259 + 843 = 96102
Step 115: 96102 + 843 = 96945
Step 116: 96945 + 843 = 97788
Step 117: 97788 + 843 = 98631
Step 118: 98631 + 843 = 99474
Step 119: 99474 + 843 = 100317
Step 120: 100317 + 843 = 101160
Step 121: 101160 + 843 = 102003
Step 122: 102003 + 843 = 102846
Step 123: 102846 + 843 = 103689
Step 124: 103689 + 843 = 104532
Step 125: 104532 + 843 = 105375
Step 126: 105375 + 843 = 106218
Step 127: 106218 + 843 = 107061
Step 128: 107061 + 843 = 107904
Step 129: 107904 + 843 = 108747
Step 130: 108747 + 843 = 109590
Step 131: 109590 + 843 = 110433
Step 132: 110433 + 843 = 111276
Step 133: 111276 + 843 = 112119
Step 134: 112119 + 843 = 112962
Step 135: 112962 + 843 = 113805
Step 136: 113805 + 843 = 114648
Step 137: 114648 + 843 = 115491
Step 138: 115491 + 843 = 116334
Step 139: 116334 + 843 = 117177
Step 140: 117177 + 843 = 118020
Step 141: 118020 + 843 = 118863
Step 142: 118863 + 843 = 119706
Step 143: 119706 + 843 = 120549

So, 843*143 = 120549