OK, let's work through this together. We're starting with 641 and we're going to multiply it by 261, which means we add 641 to itself 261 times.
Step 1: 0 + 641 = 641
Step 2: 641 + 641 = 1282
Step 3: 1282 + 641 = 1923
Step 4: 1923 + 641 = 2564
Step 5: 2564 + 641 = 3205
Step 6: 3205 + 641 = 3846
Step 7: 3846 + 641 = 4487
Step 8: 4487 + 641 = 5128
Step 9: 5128 + 641 = 5769
Step 10: 5769 + 641 = 6410
Step 11: 6410 + 641 = 7051
Step 12: 7051 + 641 = 7692
Step 13: 7692 + 641 = 8333
Step 14: 8333 + 641 = 8974
Step 15: 8974 + 641 = 9615
Step 16: 9615 + 641 = 10256
Step 17: 10256 + 641 = 10897
Step 18: 10897 + 641 = 11538
Step 19: 11538 + 641 = 12179
Step 20: 12179 + 641 = 12820
Step 21: 12820 + 641 = 13461
Step 22: 13461 + 641 = 14102
Step 23: 14102 + 641 = 14743
Step 24: 14743 + 641 = 15384
Step 25: 15384 + 641 = 16025
Step 26: 16025 + 641 = 16666
Step 27: 16666 + 641 = 17307
Step 28: 17307 + 641 = 17948
Step 29: 17948 + 641 = 18589
Step 30: 18589 + 641 = 19230
Step 31: 19230 + 641 = 19871
Step 32: 19871 + 641 = 20512
Step 33: 20512 + 641 = 21153
Step 34: 21153 + 641 = 21794
Step 35: 21794 + 641 = 22435
Step 36: 22435 + 641 = 23076
Step 37: 23076 + 641 = 23717
Step 38: 23717 + 641 = 24358
Step 39: 24358 + 641 = 24999
Step 40: 24999 + 641 = 25640
Step 41: 25640 + 641 = 26281
Step 42: 26281 + 641 = 26922
Step 43: 26922 + 641 = 27563
Step 44: 27563 + 641 = 28204
Step 45: 28204 + 641 = 28845
Step 46: 28845 + 641 = 29486
Step 47: 29486 + 641 = 30127
Step 48: 30127 + 641 = 30768
Step 49: 30768 + 641 = 31409
Step 50: 31409 + 641 = 32050
Step 51: 32050 + 641 = 32691
Step 52: 32691 + 641 = 33332
Step 53: 33332 + 641 = 33973
Step 54: 33973 + 641 = 34614
Step 55: 34614 + 641 = 35255
Step 56: 35255 + 641 = 35896
Step 57: 35896 + 641 = 36537
Step 58: 36537 + 641 = 37178
Step 59: 37178 + 641 = 37819
Step 60: 37819 + 641 = 38460
Step 61: 38460 + 641 = 39101
Step 62: 39101 + 641 = 39742
Step 63: 39742 + 641 = 40383
Step 64: 40383 + 641 = 41024
Step 65: 41024 + 641 = 41665
Step 66: 41665 + 641 = 42306
Step 67: 42306 + 641 = 42947
Step 68: 42947 + 641 = 43588
Step 69: 43588 + 641 = 44229
Step 70: 44229 + 641 = 44870
Step 71: 44870 + 641 = 45511
Step 72: 45511 + 641 = 46152
Step 73: 46152 + 641 = 46793
Step 74: 46793 + 641 = 47434
Step 75: 47434 + 641 = 48075
Step 76: 48075 + 641 = 48716
Step 77: 48716 + 641 = 49357
Step 78: 49357 + 641 = 49998
Step 79: 49998 + 641 = 50639
Step 80: 50639 + 641 = 51280
Step 81: 51280 + 641 = 51921
Step 82: 51921 + 641 = 52562
Step 83: 52562 + 641 = 53203
Step 84: 53203 + 641 = 53844
Step 85: 53844 + 641 = 54485
Step 86: 54485 + 641 = 55126
Step 87: 55126 + 641 = 55767
Step 88: 55767 + 641 = 56408
Step 89: 56408 + 641 = 57049
Step 90: 57049 + 641 = 57690
Step 91: 57690 + 641 = 58331
Step 92: 58331 + 641 = 58972
Step 93: 58972 + 641 = 59613
Step 94: 59613 + 641 = 60254
Step 95: 60254 + 641 = 60895
Step 96: 60895 + 641 = 61536
Step 97: 61536 + 641 = 62177
Step 98: 62177 + 641 = 62818
Step 99: 62818 + 641 = 63459
Step 100: 63459 + 641 = 64100
Step 101: 64100 + 641 = 64741
Step 102: 64741 + 641 = 65382
Step 103: 65382 + 641 = 66023
Step 104: 66023 + 641 = 66664
Step 105: 66664 + 641 = 67305
Step 106: 67305 + 641 = 67946
Step 107: 67946 + 641 = 68587
Step 108: 68587 + 641 = 69228
Step 109: 69228 + 641 = 69869
Step 110: 69869 + 641 = 70510
Step 111: 70510 + 641 = 71151
Step 112: 71151 + 641 = 71792
Step 113: 71792 + 641 = 72433
Step 114: 72433 + 641 = 73074
Step 115: 73074 + 641 = 73715
Step 116: 73715 + 641 = 74356
Step 117: 74356 + 641 = 74997
Step 118: 74997 + 641 = 75638
Step 119: 75638 + 641 = 76279
Step 120: 76279 + 641 = 76920
Step 121: 76920 + 641 = 77561
Step 122: 77561 + 641 = 78202
Step 123: 78202 + 641 = 78843
Step 124: 78843 + 641 = 79484
Step 125: 79484 + 641 = 80125
Step 126: 80125 + 641 = 80766
Step 127: 80766 + 641 = 81407
Step 128: 81407 + 641 = 82048
Step 129: 82048 + 641 = 82689
Step 130: 82689 + 641 = 83330
Step 131: 83330 + 641 = 83971
Step 132: 83971 + 641 = 84612
Step 133: 84612 + 641 = 85253
Step 134: 85253 + 641 = 85894
Step 135: 85894 + 641 = 86535
Step 136: 86535 + 641 = 87176
Step 137: 87176 + 641 = 87817
Step 138: 87817 + 641 = 88458
Step 139: 88458 + 641 = 89099
Step 140: 89099 + 641 = 89740
Step 141: 89740 + 641 = 90381
Step 142: 90381 + 641 = 91022
Step 143: 91022 + 641 = 91663
Step 144: 91663 + 641 = 92304
Step 145: 92304 + 641 = 92945
Step 146: 92945 + 641 = 93586
Step 147: 93586 + 641 = 94227
Step 148: 94227 + 641 = 94868
Step 149: 94868 + 641 = 95509
Step 150: 95509 + 641 = 96150
Step 151: 96150 + 641 = 96791
Step 152: 96791 + 641 = 97432
Step 153: 97432 + 641 = 98073
Step 154: 98073 + 641 = 98714
Step 155: 98714 + 641 = 99355
Step 156: 99355 + 641 = 99996
Step 157: 99996 + 641 = 100637
Step 158: 100637 + 641 = 101278
Step 159: 101278 + 641 = 101919
Step 160: 101919 + 641 = 102560
Step 161: 102560 + 641 = 103201
Step 162: 103201 + 641 = 103842
Step 163: 103842 + 641 = 104483
Step 164: 104483 + 641 = 105124
Step 165: 105124 + 641 = 105765
Step 166: 105765 + 641 = 106406
Step 167: 106406 + 641 = 107047
Step 168: 107047 + 641 = 107688
Step 169: 107688 + 641 = 108329
Step 170: 108329 + 641 = 108970
Step 171: 108970 + 641 = 109611
Step 172: 109611 + 641 = 110252
Step 173: 110252 + 641 = 110893
Step 174: 110893 + 641 = 111534
Step 175: 111534 + 641 = 112175
Step 176: 112175 + 641 = 112816
Step 177: 112816 + 641 = 113457
Step 178: 113457 + 641 = 114098
Step 179: 114098 + 641 = 114739
Step 180: 114739 + 641 = 115380
Step 181: 115380 + 641 = 116021
Step 182: 116021 + 641 = 116662
Step 183: 116662 + 641 = 117303
Step 184: 117303 + 641 = 117944
Step 185: 117944 + 641 = 118585
Step 186: 118585 + 641 = 119226
Step 187: 119226 + 641 = 119867
Step 188: 119867 + 641 = 120508
Step 189: 120508 + 641 = 121149
Step 190: 121149 + 641 = 121790
Step 191: 121790 + 641 = 122431
Step 192: 122431 + 641 = 123072
Step 193: 123072 + 641 = 123713
Step 194: 123713 + 641 = 124354
Step 195: 124354 + 641 = 124995
Step 196: 124995 + 641 = 125636
Step 197: 125636 + 641 = 126277
Step 198: 126277 + 641 = 126918
Step 199: 126918 + 641 = 127559
Step 200: 127559 + 641 = 128200
Step 201: 128200 + 641 = 128841
Step 202: 128841 + 641 = 129482
Step 203: 129482 + 641 = 130123
Step 204: 130123 + 641 = 130764
Step 205: 130764 + 641 = 131405
Step 206: 131405 + 641 = 132046
Step 207: 132046 + 641 = 132687
Step 208: 132687 + 641 = 133328
Step 209: 133328 + 641 = 133969
Step 210: 133969 + 641 = 134610
Step 211: 134610 + 641 = 135251
Step 212: 135251 + 641 = 135892
Step 213: 135892 + 641 = 136533
Step 214: 136533 + 641 = 137174
Step 215: 137174 + 641 = 137815
Step 216: 137815 + 641 = 138456
Step 217: 138456 + 641 = 139097
Step 218: 139097 + 641 = 139738
Step 219: 139738 + 641 = 140379
Step 220: 140379 + 641 = 141020
Step 221: 141020 + 641 = 141661
Step 222: 141661 + 641 = 142302
Step 223: 142302 + 641 = 142943
Step 224: 142943 + 641 = 143584
Step 225: 143584 + 641 = 144225
Step 226: 144225 + 641 = 144866
Step 227: 144866 + 641 = 145507
Step 228: 145507 + 641 = 146148
Step 229: 146148 + 641 = 146789
Step 230: 146789 + 641 = 147430
Step 231: 147430 + 641 = 148071
Step 232: 148071 + 641 = 148712
Step 233: 148712 + 641 = 149353
Step 234: 149353 + 641 = 149994
Step 235: 149994 + 641 = 150635
Step 236: 150635 + 641 = 151276
Step 237: 151276 + 641 = 151917
Step 238: 151917 + 641 = 152558
Step 239: 152558 + 641 = 153199
Step 240: 153199 + 641 = 153840
Step 241: 153840 + 641 = 154481
Step 242: 154481 + 641 = 155122
Step 243: 155122 + 641 = 155763
Step 244: 155763 + 641 = 156404
Step 245: 156404 + 641 = 157045
Step 246: 157045 + 641 = 157686
Step 247: 157686 + 641 = 158327
Step 248: 158327 + 641 = 158968
Step 249: 158968 + 641 = 159609
Step 250: 159609 + 641 = 160250
Step 251: 160250 + 641 = 160891
Step 252: 160891 + 641 = 161532
Step 253: 161532 + 641 = 162173
Step 254: 162173 + 641 = 162814
Step 255: 162814 + 641 = 163455
Step 256: 163455 + 641 = 164096
Step 257: 164096 + 641 = 164737
Step 258: 164737 + 641 = 165378
Step 259: 165378 + 641 = 166019
Step 260: 166019 + 641 = 166660
Step 261: 166660 + 641 = 167301

So, 641*261 = 167301