Alright, let's solve this math problem step by step. First, we have the number 21. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 166. So, we're going to take the number 21 and add it to itself 166 times.
Step 1: 0 + 21 = 21
Step 2: 21 + 21 = 42
Step 3: 42 + 21 = 63
Step 4: 63 + 21 = 84
Step 5: 84 + 21 = 105
Step 6: 105 + 21 = 126
Step 7: 126 + 21 = 147
Step 8: 147 + 21 = 168
Step 9: 168 + 21 = 189
Step 10: 189 + 21 = 210
Step 11: 210 + 21 = 231
Step 12: 231 + 21 = 252
Step 13: 252 + 21 = 273
Step 14: 273 + 21 = 294
Step 15: 294 + 21 = 315
Step 16: 315 + 21 = 336
Step 17: 336 + 21 = 357
Step 18: 357 + 21 = 378
Step 19: 378 + 21 = 399
Step 20: 399 + 21 = 420
Step 21: 420 + 21 = 441
Step 22: 441 + 21 = 462
Step 23: 462 + 21 = 483
Step 24: 483 + 21 = 504
Step 25: 504 + 21 = 525
Step 26: 525 + 21 = 546
Step 27: 546 + 21 = 567
Step 28: 567 + 21 = 588
Step 29: 588 + 21 = 609
Step 30: 609 + 21 = 630
Step 31: 630 + 21 = 651
Step 32: 651 + 21 = 672
Step 33: 672 + 21 = 693
Step 34: 693 + 21 = 714
Step 35: 714 + 21 = 735
Step 36: 735 + 21 = 756
Step 37: 756 + 21 = 777
Step 38: 777 + 21 = 798
Step 39: 798 + 21 = 819
Step 40: 819 + 21 = 840
Step 41: 840 + 21 = 861
Step 42: 861 + 21 = 882
Step 43: 882 + 21 = 903
Step 44: 903 + 21 = 924
Step 45: 924 + 21 = 945
Step 46: 945 + 21 = 966
Step 47: 966 + 21 = 987
Step 48: 987 + 21 = 1008
Step 49: 1008 + 21 = 1029
Step 50: 1029 + 21 = 1050
Step 51: 1050 + 21 = 1071
Step 52: 1071 + 21 = 1092
Step 53: 1092 + 21 = 1113
Step 54: 1113 + 21 = 1134
Step 55: 1134 + 21 = 1155
Step 56: 1155 + 21 = 1176
Step 57: 1176 + 21 = 1197
Step 58: 1197 + 21 = 1218
Step 59: 1218 + 21 = 1239
Step 60: 1239 + 21 = 1260
Step 61: 1260 + 21 = 1281
Step 62: 1281 + 21 = 1302
Step 63: 1302 + 21 = 1323
Step 64: 1323 + 21 = 1344
Step 65: 1344 + 21 = 1365
Step 66: 1365 + 21 = 1386
Step 67: 1386 + 21 = 1407
Step 68: 1407 + 21 = 1428
Step 69: 1428 + 21 = 1449
Step 70: 1449 + 21 = 1470
Step 71: 1470 + 21 = 1491
Step 72: 1491 + 21 = 1512
Step 73: 1512 + 21 = 1533
Step 74: 1533 + 21 = 1554
Step 75: 1554 + 21 = 1575
Step 76: 1575 + 21 = 1596
Step 77: 1596 + 21 = 1617
Step 78: 1617 + 21 = 1638
Step 79: 1638 + 21 = 1659
Step 80: 1659 + 21 = 1680
Step 81: 1680 + 21 = 1701
Step 82: 1701 + 21 = 1722
Step 83: 1722 + 21 = 1743
Step 84: 1743 + 21 = 1764
Step 85: 1764 + 21 = 1785
Step 86: 1785 + 21 = 1806
Step 87: 1806 + 21 = 1827
Step 88: 1827 + 21 = 1848
Step 89: 1848 + 21 = 1869
Step 90: 1869 + 21 = 1890
Step 91: 1890 + 21 = 1911
Step 92: 1911 + 21 = 1932
Step 93: 1932 + 21 = 1953
Step 94: 1953 + 21 = 1974
Step 95: 1974 + 21 = 1995
Step 96: 1995 + 21 = 2016
Step 97: 2016 + 21 = 2037
Step 98: 2037 + 21 = 2058
Step 99: 2058 + 21 = 2079
Step 100: 2079 + 21 = 2100
Step 101: 2100 + 21 = 2121
Step 102: 2121 + 21 = 2142
Step 103: 2142 + 21 = 2163
Step 104: 2163 + 21 = 2184
Step 105: 2184 + 21 = 2205
Step 106: 2205 + 21 = 2226
Step 107: 2226 + 21 = 2247
Step 108: 2247 + 21 = 2268
Step 109: 2268 + 21 = 2289
Step 110: 2289 + 21 = 2310
Step 111: 2310 + 21 = 2331
Step 112: 2331 + 21 = 2352
Step 113: 2352 + 21 = 2373
Step 114: 2373 + 21 = 2394
Step 115: 2394 + 21 = 2415
Step 116: 2415 + 21 = 2436
Step 117: 2436 + 21 = 2457
Step 118: 2457 + 21 = 2478
Step 119: 2478 + 21 = 2499
Step 120: 2499 + 21 = 2520
Step 121: 2520 + 21 = 2541
Step 122: 2541 + 21 = 2562
Step 123: 2562 + 21 = 2583
Step 124: 2583 + 21 = 2604
Step 125: 2604 + 21 = 2625
Step 126: 2625 + 21 = 2646
Step 127: 2646 + 21 = 2667
Step 128: 2667 + 21 = 2688
Step 129: 2688 + 21 = 2709
Step 130: 2709 + 21 = 2730
Step 131: 2730 + 21 = 2751
Step 132: 2751 + 21 = 2772
Step 133: 2772 + 21 = 2793
Step 134: 2793 + 21 = 2814
Step 135: 2814 + 21 = 2835
Step 136: 2835 + 21 = 2856
Step 137: 2856 + 21 = 2877
Step 138: 2877 + 21 = 2898
Step 139: 2898 + 21 = 2919
Step 140: 2919 + 21 = 2940
Step 141: 2940 + 21 = 2961
Step 142: 2961 + 21 = 2982
Step 143: 2982 + 21 = 3003
Step 144: 3003 + 21 = 3024
Step 145: 3024 + 21 = 3045
Step 146: 3045 + 21 = 3066
Step 147: 3066 + 21 = 3087
Step 148: 3087 + 21 = 3108
Step 149: 3108 + 21 = 3129
Step 150: 3129 + 21 = 3150
Step 151: 3150 + 21 = 3171
Step 152: 3171 + 21 = 3192
Step 153: 3192 + 21 = 3213
Step 154: 3213 + 21 = 3234
Step 155: 3234 + 21 = 3255
Step 156: 3255 + 21 = 3276
Step 157: 3276 + 21 = 3297
Step 158: 3297 + 21 = 3318
Step 159: 3318 + 21 = 3339
Step 160: 3339 + 21 = 3360
Step 161: 3360 + 21 = 3381
Step 162: 3381 + 21 = 3402
Step 163: 3402 + 21 = 3423
Step 164: 3423 + 21 = 3444
Step 165: 3444 + 21 = 3465
Step 166: 3465 + 21 = 3486

So, 21*166 = 3486