Alright, let's solve this math problem step by step. First, we have the number 645. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 107. So, we're going to take the number 645 and add it to itself 107 times.
Step 1: 0 + 645 = 645
Step 2: 645 + 645 = 1290
Step 3: 1290 + 645 = 1935
Step 4: 1935 + 645 = 2580
Step 5: 2580 + 645 = 3225
Step 6: 3225 + 645 = 3870
Step 7: 3870 + 645 = 4515
Step 8: 4515 + 645 = 5160
Step 9: 5160 + 645 = 5805
Step 10: 5805 + 645 = 6450
Step 11: 6450 + 645 = 7095
Step 12: 7095 + 645 = 7740
Step 13: 7740 + 645 = 8385
Step 14: 8385 + 645 = 9030
Step 15: 9030 + 645 = 9675
Step 16: 9675 + 645 = 10320
Step 17: 10320 + 645 = 10965
Step 18: 10965 + 645 = 11610
Step 19: 11610 + 645 = 12255
Step 20: 12255 + 645 = 12900
Step 21: 12900 + 645 = 13545
Step 22: 13545 + 645 = 14190
Step 23: 14190 + 645 = 14835
Step 24: 14835 + 645 = 15480
Step 25: 15480 + 645 = 16125
Step 26: 16125 + 645 = 16770
Step 27: 16770 + 645 = 17415
Step 28: 17415 + 645 = 18060
Step 29: 18060 + 645 = 18705
Step 30: 18705 + 645 = 19350
Step 31: 19350 + 645 = 19995
Step 32: 19995 + 645 = 20640
Step 33: 20640 + 645 = 21285
Step 34: 21285 + 645 = 21930
Step 35: 21930 + 645 = 22575
Step 36: 22575 + 645 = 23220
Step 37: 23220 + 645 = 23865
Step 38: 23865 + 645 = 24510
Step 39: 24510 + 645 = 25155
Step 40: 25155 + 645 = 25800
Step 41: 25800 + 645 = 26445
Step 42: 26445 + 645 = 27090
Step 43: 27090 + 645 = 27735
Step 44: 27735 + 645 = 28380
Step 45: 28380 + 645 = 29025
Step 46: 29025 + 645 = 29670
Step 47: 29670 + 645 = 30315
Step 48: 30315 + 645 = 30960
Step 49: 30960 + 645 = 31605
Step 50: 31605 + 645 = 32250
Step 51: 32250 + 645 = 32895
Step 52: 32895 + 645 = 33540
Step 53: 33540 + 645 = 34185
Step 54: 34185 + 645 = 34830
Step 55: 34830 + 645 = 35475
Step 56: 35475 + 645 = 36120
Step 57: 36120 + 645 = 36765
Step 58: 36765 + 645 = 37410
Step 59: 37410 + 645 = 38055
Step 60: 38055 + 645 = 38700
Step 61: 38700 + 645 = 39345
Step 62: 39345 + 645 = 39990
Step 63: 39990 + 645 = 40635
Step 64: 40635 + 645 = 41280
Step 65: 41280 + 645 = 41925
Step 66: 41925 + 645 = 42570
Step 67: 42570 + 645 = 43215
Step 68: 43215 + 645 = 43860
Step 69: 43860 + 645 = 44505
Step 70: 44505 + 645 = 45150
Step 71: 45150 + 645 = 45795
Step 72: 45795 + 645 = 46440
Step 73: 46440 + 645 = 47085
Step 74: 47085 + 645 = 47730
Step 75: 47730 + 645 = 48375
Step 76: 48375 + 645 = 49020
Step 77: 49020 + 645 = 49665
Step 78: 49665 + 645 = 50310
Step 79: 50310 + 645 = 50955
Step 80: 50955 + 645 = 51600
Step 81: 51600 + 645 = 52245
Step 82: 52245 + 645 = 52890
Step 83: 52890 + 645 = 53535
Step 84: 53535 + 645 = 54180
Step 85: 54180 + 645 = 54825
Step 86: 54825 + 645 = 55470
Step 87: 55470 + 645 = 56115
Step 88: 56115 + 645 = 56760
Step 89: 56760 + 645 = 57405
Step 90: 57405 + 645 = 58050
Step 91: 58050 + 645 = 58695
Step 92: 58695 + 645 = 59340
Step 93: 59340 + 645 = 59985
Step 94: 59985 + 645 = 60630
Step 95: 60630 + 645 = 61275
Step 96: 61275 + 645 = 61920
Step 97: 61920 + 645 = 62565
Step 98: 62565 + 645 = 63210
Step 99: 63210 + 645 = 63855
Step 100: 63855 + 645 = 64500
Step 101: 64500 + 645 = 65145
Step 102: 65145 + 645 = 65790
Step 103: 65790 + 645 = 66435
Step 104: 66435 + 645 = 67080
Step 105: 67080 + 645 = 67725
Step 106: 67725 + 645 = 68370
Step 107: 68370 + 645 = 69015

So, 645*107 = 69015