OK, let's crack this. We're given 909 and our task is to multiply it by 80. Essentially, we'll be adding 909 to itself 80 times.
Step 1: 0 + 909 = 909
Step 2: 909 + 909 = 1818
Step 3: 1818 + 909 = 2727
Step 4: 2727 + 909 = 3636
Step 5: 3636 + 909 = 4545
Step 6: 4545 + 909 = 5454
Step 7: 5454 + 909 = 6363
Step 8: 6363 + 909 = 7272
Step 9: 7272 + 909 = 8181
Step 10: 8181 + 909 = 9090
Step 11: 9090 + 909 = 9999
Step 12: 9999 + 909 = 10908
Step 13: 10908 + 909 = 11817
Step 14: 11817 + 909 = 12726
Step 15: 12726 + 909 = 13635
Step 16: 13635 + 909 = 14544
Step 17: 14544 + 909 = 15453
Step 18: 15453 + 909 = 16362
Step 19: 16362 + 909 = 17271
Step 20: 17271 + 909 = 18180
Step 21: 18180 + 909 = 19089
Step 22: 19089 + 909 = 19998
Step 23: 19998 + 909 = 20907
Step 24: 20907 + 909 = 21816
Step 25: 21816 + 909 = 22725
Step 26: 22725 + 909 = 23634
Step 27: 23634 + 909 = 24543
Step 28: 24543 + 909 = 25452
Step 29: 25452 + 909 = 26361
Step 30: 26361 + 909 = 27270
Step 31: 27270 + 909 = 28179
Step 32: 28179 + 909 = 29088
Step 33: 29088 + 909 = 29997
Step 34: 29997 + 909 = 30906
Step 35: 30906 + 909 = 31815
Step 36: 31815 + 909 = 32724
Step 37: 32724 + 909 = 33633
Step 38: 33633 + 909 = 34542
Step 39: 34542 + 909 = 35451
Step 40: 35451 + 909 = 36360
Step 41: 36360 + 909 = 37269
Step 42: 37269 + 909 = 38178
Step 43: 38178 + 909 = 39087
Step 44: 39087 + 909 = 39996
Step 45: 39996 + 909 = 40905
Step 46: 40905 + 909 = 41814
Step 47: 41814 + 909 = 42723
Step 48: 42723 + 909 = 43632
Step 49: 43632 + 909 = 44541
Step 50: 44541 + 909 = 45450
Step 51: 45450 + 909 = 46359
Step 52: 46359 + 909 = 47268
Step 53: 47268 + 909 = 48177
Step 54: 48177 + 909 = 49086
Step 55: 49086 + 909 = 49995
Step 56: 49995 + 909 = 50904
Step 57: 50904 + 909 = 51813
Step 58: 51813 + 909 = 52722
Step 59: 52722 + 909 = 53631
Step 60: 53631 + 909 = 54540
Step 61: 54540 + 909 = 55449
Step 62: 55449 + 909 = 56358
Step 63: 56358 + 909 = 57267
Step 64: 57267 + 909 = 58176
Step 65: 58176 + 909 = 59085
Step 66: 59085 + 909 = 59994
Step 67: 59994 + 909 = 60903
Step 68: 60903 + 909 = 61812
Step 69: 61812 + 909 = 62721
Step 70: 62721 + 909 = 63630
Step 71: 63630 + 909 = 64539
Step 72: 64539 + 909 = 65448
Step 73: 65448 + 909 = 66357
Step 74: 66357 + 909 = 67266
Step 75: 67266 + 909 = 68175
Step 76: 68175 + 909 = 69084
Step 77: 69084 + 909 = 69993
Step 78: 69993 + 909 = 70902
Step 79: 70902 + 909 = 71811
Step 80: 71811 + 909 = 72720

So, 909*80 = 72720