OK, let's crack this. We're given 670 and our task is to multiply it by 102. Essentially, we'll be adding 670 to itself 102 times.
Step 1: 0 + 670 = 670
Step 2: 670 + 670 = 1340
Step 3: 1340 + 670 = 2010
Step 4: 2010 + 670 = 2680
Step 5: 2680 + 670 = 3350
Step 6: 3350 + 670 = 4020
Step 7: 4020 + 670 = 4690
Step 8: 4690 + 670 = 5360
Step 9: 5360 + 670 = 6030
Step 10: 6030 + 670 = 6700
Step 11: 6700 + 670 = 7370
Step 12: 7370 + 670 = 8040
Step 13: 8040 + 670 = 8710
Step 14: 8710 + 670 = 9380
Step 15: 9380 + 670 = 10050
Step 16: 10050 + 670 = 10720
Step 17: 10720 + 670 = 11390
Step 18: 11390 + 670 = 12060
Step 19: 12060 + 670 = 12730
Step 20: 12730 + 670 = 13400
Step 21: 13400 + 670 = 14070
Step 22: 14070 + 670 = 14740
Step 23: 14740 + 670 = 15410
Step 24: 15410 + 670 = 16080
Step 25: 16080 + 670 = 16750
Step 26: 16750 + 670 = 17420
Step 27: 17420 + 670 = 18090
Step 28: 18090 + 670 = 18760
Step 29: 18760 + 670 = 19430
Step 30: 19430 + 670 = 20100
Step 31: 20100 + 670 = 20770
Step 32: 20770 + 670 = 21440
Step 33: 21440 + 670 = 22110
Step 34: 22110 + 670 = 22780
Step 35: 22780 + 670 = 23450
Step 36: 23450 + 670 = 24120
Step 37: 24120 + 670 = 24790
Step 38: 24790 + 670 = 25460
Step 39: 25460 + 670 = 26130
Step 40: 26130 + 670 = 26800
Step 41: 26800 + 670 = 27470
Step 42: 27470 + 670 = 28140
Step 43: 28140 + 670 = 28810
Step 44: 28810 + 670 = 29480
Step 45: 29480 + 670 = 30150
Step 46: 30150 + 670 = 30820
Step 47: 30820 + 670 = 31490
Step 48: 31490 + 670 = 32160
Step 49: 32160 + 670 = 32830
Step 50: 32830 + 670 = 33500
Step 51: 33500 + 670 = 34170
Step 52: 34170 + 670 = 34840
Step 53: 34840 + 670 = 35510
Step 54: 35510 + 670 = 36180
Step 55: 36180 + 670 = 36850
Step 56: 36850 + 670 = 37520
Step 57: 37520 + 670 = 38190
Step 58: 38190 + 670 = 38860
Step 59: 38860 + 670 = 39530
Step 60: 39530 + 670 = 40200
Step 61: 40200 + 670 = 40870
Step 62: 40870 + 670 = 41540
Step 63: 41540 + 670 = 42210
Step 64: 42210 + 670 = 42880
Step 65: 42880 + 670 = 43550
Step 66: 43550 + 670 = 44220
Step 67: 44220 + 670 = 44890
Step 68: 44890 + 670 = 45560
Step 69: 45560 + 670 = 46230
Step 70: 46230 + 670 = 46900
Step 71: 46900 + 670 = 47570
Step 72: 47570 + 670 = 48240
Step 73: 48240 + 670 = 48910
Step 74: 48910 + 670 = 49580
Step 75: 49580 + 670 = 50250
Step 76: 50250 + 670 = 50920
Step 77: 50920 + 670 = 51590
Step 78: 51590 + 670 = 52260
Step 79: 52260 + 670 = 52930
Step 80: 52930 + 670 = 53600
Step 81: 53600 + 670 = 54270
Step 82: 54270 + 670 = 54940
Step 83: 54940 + 670 = 55610
Step 84: 55610 + 670 = 56280
Step 85: 56280 + 670 = 56950
Step 86: 56950 + 670 = 57620
Step 87: 57620 + 670 = 58290
Step 88: 58290 + 670 = 58960
Step 89: 58960 + 670 = 59630
Step 90: 59630 + 670 = 60300
Step 91: 60300 + 670 = 60970
Step 92: 60970 + 670 = 61640
Step 93: 61640 + 670 = 62310
Step 94: 62310 + 670 = 62980
Step 95: 62980 + 670 = 63650
Step 96: 63650 + 670 = 64320
Step 97: 64320 + 670 = 64990
Step 98: 64990 + 670 = 65660
Step 99: 65660 + 670 = 66330
Step 100: 66330 + 670 = 67000
Step 101: 67000 + 670 = 67670
Step 102: 67670 + 670 = 68340

So, 670*102 = 68340