OK, let's crack this. We're given 815 and our task is to multiply it by 70. Essentially, we'll be adding 815 to itself 70 times.
Step 1: 0 + 815 = 815
Step 2: 815 + 815 = 1630
Step 3: 1630 + 815 = 2445
Step 4: 2445 + 815 = 3260
Step 5: 3260 + 815 = 4075
Step 6: 4075 + 815 = 4890
Step 7: 4890 + 815 = 5705
Step 8: 5705 + 815 = 6520
Step 9: 6520 + 815 = 7335
Step 10: 7335 + 815 = 8150
Step 11: 8150 + 815 = 8965
Step 12: 8965 + 815 = 9780
Step 13: 9780 + 815 = 10595
Step 14: 10595 + 815 = 11410
Step 15: 11410 + 815 = 12225
Step 16: 12225 + 815 = 13040
Step 17: 13040 + 815 = 13855
Step 18: 13855 + 815 = 14670
Step 19: 14670 + 815 = 15485
Step 20: 15485 + 815 = 16300
Step 21: 16300 + 815 = 17115
Step 22: 17115 + 815 = 17930
Step 23: 17930 + 815 = 18745
Step 24: 18745 + 815 = 19560
Step 25: 19560 + 815 = 20375
Step 26: 20375 + 815 = 21190
Step 27: 21190 + 815 = 22005
Step 28: 22005 + 815 = 22820
Step 29: 22820 + 815 = 23635
Step 30: 23635 + 815 = 24450
Step 31: 24450 + 815 = 25265
Step 32: 25265 + 815 = 26080
Step 33: 26080 + 815 = 26895
Step 34: 26895 + 815 = 27710
Step 35: 27710 + 815 = 28525
Step 36: 28525 + 815 = 29340
Step 37: 29340 + 815 = 30155
Step 38: 30155 + 815 = 30970
Step 39: 30970 + 815 = 31785
Step 40: 31785 + 815 = 32600
Step 41: 32600 + 815 = 33415
Step 42: 33415 + 815 = 34230
Step 43: 34230 + 815 = 35045
Step 44: 35045 + 815 = 35860
Step 45: 35860 + 815 = 36675
Step 46: 36675 + 815 = 37490
Step 47: 37490 + 815 = 38305
Step 48: 38305 + 815 = 39120
Step 49: 39120 + 815 = 39935
Step 50: 39935 + 815 = 40750
Step 51: 40750 + 815 = 41565
Step 52: 41565 + 815 = 42380
Step 53: 42380 + 815 = 43195
Step 54: 43195 + 815 = 44010
Step 55: 44010 + 815 = 44825
Step 56: 44825 + 815 = 45640
Step 57: 45640 + 815 = 46455
Step 58: 46455 + 815 = 47270
Step 59: 47270 + 815 = 48085
Step 60: 48085 + 815 = 48900
Step 61: 48900 + 815 = 49715
Step 62: 49715 + 815 = 50530
Step 63: 50530 + 815 = 51345
Step 64: 51345 + 815 = 52160
Step 65: 52160 + 815 = 52975
Step 66: 52975 + 815 = 53790
Step 67: 53790 + 815 = 54605
Step 68: 54605 + 815 = 55420
Step 69: 55420 + 815 = 56235
Step 70: 56235 + 815 = 57050

So, 815*70 = 57050