OK, let's work through this together. We're starting with 905 and we're going to multiply it by 79, which means we add 905 to itself 79 times.
Step 1: 0 + 905 = 905
Step 2: 905 + 905 = 1810
Step 3: 1810 + 905 = 2715
Step 4: 2715 + 905 = 3620
Step 5: 3620 + 905 = 4525
Step 6: 4525 + 905 = 5430
Step 7: 5430 + 905 = 6335
Step 8: 6335 + 905 = 7240
Step 9: 7240 + 905 = 8145
Step 10: 8145 + 905 = 9050
Step 11: 9050 + 905 = 9955
Step 12: 9955 + 905 = 10860
Step 13: 10860 + 905 = 11765
Step 14: 11765 + 905 = 12670
Step 15: 12670 + 905 = 13575
Step 16: 13575 + 905 = 14480
Step 17: 14480 + 905 = 15385
Step 18: 15385 + 905 = 16290
Step 19: 16290 + 905 = 17195
Step 20: 17195 + 905 = 18100
Step 21: 18100 + 905 = 19005
Step 22: 19005 + 905 = 19910
Step 23: 19910 + 905 = 20815
Step 24: 20815 + 905 = 21720
Step 25: 21720 + 905 = 22625
Step 26: 22625 + 905 = 23530
Step 27: 23530 + 905 = 24435
Step 28: 24435 + 905 = 25340
Step 29: 25340 + 905 = 26245
Step 30: 26245 + 905 = 27150
Step 31: 27150 + 905 = 28055
Step 32: 28055 + 905 = 28960
Step 33: 28960 + 905 = 29865
Step 34: 29865 + 905 = 30770
Step 35: 30770 + 905 = 31675
Step 36: 31675 + 905 = 32580
Step 37: 32580 + 905 = 33485
Step 38: 33485 + 905 = 34390
Step 39: 34390 + 905 = 35295
Step 40: 35295 + 905 = 36200
Step 41: 36200 + 905 = 37105
Step 42: 37105 + 905 = 38010
Step 43: 38010 + 905 = 38915
Step 44: 38915 + 905 = 39820
Step 45: 39820 + 905 = 40725
Step 46: 40725 + 905 = 41630
Step 47: 41630 + 905 = 42535
Step 48: 42535 + 905 = 43440
Step 49: 43440 + 905 = 44345
Step 50: 44345 + 905 = 45250
Step 51: 45250 + 905 = 46155
Step 52: 46155 + 905 = 47060
Step 53: 47060 + 905 = 47965
Step 54: 47965 + 905 = 48870
Step 55: 48870 + 905 = 49775
Step 56: 49775 + 905 = 50680
Step 57: 50680 + 905 = 51585
Step 58: 51585 + 905 = 52490
Step 59: 52490 + 905 = 53395
Step 60: 53395 + 905 = 54300
Step 61: 54300 + 905 = 55205
Step 62: 55205 + 905 = 56110
Step 63: 56110 + 905 = 57015
Step 64: 57015 + 905 = 57920
Step 65: 57920 + 905 = 58825
Step 66: 58825 + 905 = 59730
Step 67: 59730 + 905 = 60635
Step 68: 60635 + 905 = 61540
Step 69: 61540 + 905 = 62445
Step 70: 62445 + 905 = 63350
Step 71: 63350 + 905 = 64255
Step 72: 64255 + 905 = 65160
Step 73: 65160 + 905 = 66065
Step 74: 66065 + 905 = 66970
Step 75: 66970 + 905 = 67875
Step 76: 67875 + 905 = 68780
Step 77: 68780 + 905 = 69685
Step 78: 69685 + 905 = 70590
Step 79: 70590 + 905 = 71495

So, 905*79 = 71495