Without delay, let's solve this. We've got 866 and we will be multiplying it by 91, that is, adding 866 to itself 91 times.
Step 1: 0 + 866 = 866
Step 2: 866 + 866 = 1732
Step 3: 1732 + 866 = 2598
Step 4: 2598 + 866 = 3464
Step 5: 3464 + 866 = 4330
Step 6: 4330 + 866 = 5196
Step 7: 5196 + 866 = 6062
Step 8: 6062 + 866 = 6928
Step 9: 6928 + 866 = 7794
Step 10: 7794 + 866 = 8660
Step 11: 8660 + 866 = 9526
Step 12: 9526 + 866 = 10392
Step 13: 10392 + 866 = 11258
Step 14: 11258 + 866 = 12124
Step 15: 12124 + 866 = 12990
Step 16: 12990 + 866 = 13856
Step 17: 13856 + 866 = 14722
Step 18: 14722 + 866 = 15588
Step 19: 15588 + 866 = 16454
Step 20: 16454 + 866 = 17320
Step 21: 17320 + 866 = 18186
Step 22: 18186 + 866 = 19052
Step 23: 19052 + 866 = 19918
Step 24: 19918 + 866 = 20784
Step 25: 20784 + 866 = 21650
Step 26: 21650 + 866 = 22516
Step 27: 22516 + 866 = 23382
Step 28: 23382 + 866 = 24248
Step 29: 24248 + 866 = 25114
Step 30: 25114 + 866 = 25980
Step 31: 25980 + 866 = 26846
Step 32: 26846 + 866 = 27712
Step 33: 27712 + 866 = 28578
Step 34: 28578 + 866 = 29444
Step 35: 29444 + 866 = 30310
Step 36: 30310 + 866 = 31176
Step 37: 31176 + 866 = 32042
Step 38: 32042 + 866 = 32908
Step 39: 32908 + 866 = 33774
Step 40: 33774 + 866 = 34640
Step 41: 34640 + 866 = 35506
Step 42: 35506 + 866 = 36372
Step 43: 36372 + 866 = 37238
Step 44: 37238 + 866 = 38104
Step 45: 38104 + 866 = 38970
Step 46: 38970 + 866 = 39836
Step 47: 39836 + 866 = 40702
Step 48: 40702 + 866 = 41568
Step 49: 41568 + 866 = 42434
Step 50: 42434 + 866 = 43300
Step 51: 43300 + 866 = 44166
Step 52: 44166 + 866 = 45032
Step 53: 45032 + 866 = 45898
Step 54: 45898 + 866 = 46764
Step 55: 46764 + 866 = 47630
Step 56: 47630 + 866 = 48496
Step 57: 48496 + 866 = 49362
Step 58: 49362 + 866 = 50228
Step 59: 50228 + 866 = 51094
Step 60: 51094 + 866 = 51960
Step 61: 51960 + 866 = 52826
Step 62: 52826 + 866 = 53692
Step 63: 53692 + 866 = 54558
Step 64: 54558 + 866 = 55424
Step 65: 55424 + 866 = 56290
Step 66: 56290 + 866 = 57156
Step 67: 57156 + 866 = 58022
Step 68: 58022 + 866 = 58888
Step 69: 58888 + 866 = 59754
Step 70: 59754 + 866 = 60620
Step 71: 60620 + 866 = 61486
Step 72: 61486 + 866 = 62352
Step 73: 62352 + 866 = 63218
Step 74: 63218 + 866 = 64084
Step 75: 64084 + 866 = 64950
Step 76: 64950 + 866 = 65816
Step 77: 65816 + 866 = 66682
Step 78: 66682 + 866 = 67548
Step 79: 67548 + 866 = 68414
Step 80: 68414 + 866 = 69280
Step 81: 69280 + 866 = 70146
Step 82: 70146 + 866 = 71012
Step 83: 71012 + 866 = 71878
Step 84: 71878 + 866 = 72744
Step 85: 72744 + 866 = 73610
Step 86: 73610 + 866 = 74476
Step 87: 74476 + 866 = 75342
Step 88: 75342 + 866 = 76208
Step 89: 76208 + 866 = 77074
Step 90: 77074 + 866 = 77940
Step 91: 77940 + 866 = 78806

So, 866*91 = 78806