Let's roll up our sleeves and solve this. We have 842 and we're going to multiply it by 89, essentially adding 842 to itself 89 times.
Step 1: 0 + 842 = 842
Step 2: 842 + 842 = 1684
Step 3: 1684 + 842 = 2526
Step 4: 2526 + 842 = 3368
Step 5: 3368 + 842 = 4210
Step 6: 4210 + 842 = 5052
Step 7: 5052 + 842 = 5894
Step 8: 5894 + 842 = 6736
Step 9: 6736 + 842 = 7578
Step 10: 7578 + 842 = 8420
Step 11: 8420 + 842 = 9262
Step 12: 9262 + 842 = 10104
Step 13: 10104 + 842 = 10946
Step 14: 10946 + 842 = 11788
Step 15: 11788 + 842 = 12630
Step 16: 12630 + 842 = 13472
Step 17: 13472 + 842 = 14314
Step 18: 14314 + 842 = 15156
Step 19: 15156 + 842 = 15998
Step 20: 15998 + 842 = 16840
Step 21: 16840 + 842 = 17682
Step 22: 17682 + 842 = 18524
Step 23: 18524 + 842 = 19366
Step 24: 19366 + 842 = 20208
Step 25: 20208 + 842 = 21050
Step 26: 21050 + 842 = 21892
Step 27: 21892 + 842 = 22734
Step 28: 22734 + 842 = 23576
Step 29: 23576 + 842 = 24418
Step 30: 24418 + 842 = 25260
Step 31: 25260 + 842 = 26102
Step 32: 26102 + 842 = 26944
Step 33: 26944 + 842 = 27786
Step 34: 27786 + 842 = 28628
Step 35: 28628 + 842 = 29470
Step 36: 29470 + 842 = 30312
Step 37: 30312 + 842 = 31154
Step 38: 31154 + 842 = 31996
Step 39: 31996 + 842 = 32838
Step 40: 32838 + 842 = 33680
Step 41: 33680 + 842 = 34522
Step 42: 34522 + 842 = 35364
Step 43: 35364 + 842 = 36206
Step 44: 36206 + 842 = 37048
Step 45: 37048 + 842 = 37890
Step 46: 37890 + 842 = 38732
Step 47: 38732 + 842 = 39574
Step 48: 39574 + 842 = 40416
Step 49: 40416 + 842 = 41258
Step 50: 41258 + 842 = 42100
Step 51: 42100 + 842 = 42942
Step 52: 42942 + 842 = 43784
Step 53: 43784 + 842 = 44626
Step 54: 44626 + 842 = 45468
Step 55: 45468 + 842 = 46310
Step 56: 46310 + 842 = 47152
Step 57: 47152 + 842 = 47994
Step 58: 47994 + 842 = 48836
Step 59: 48836 + 842 = 49678
Step 60: 49678 + 842 = 50520
Step 61: 50520 + 842 = 51362
Step 62: 51362 + 842 = 52204
Step 63: 52204 + 842 = 53046
Step 64: 53046 + 842 = 53888
Step 65: 53888 + 842 = 54730
Step 66: 54730 + 842 = 55572
Step 67: 55572 + 842 = 56414
Step 68: 56414 + 842 = 57256
Step 69: 57256 + 842 = 58098
Step 70: 58098 + 842 = 58940
Step 71: 58940 + 842 = 59782
Step 72: 59782 + 842 = 60624
Step 73: 60624 + 842 = 61466
Step 74: 61466 + 842 = 62308
Step 75: 62308 + 842 = 63150
Step 76: 63150 + 842 = 63992
Step 77: 63992 + 842 = 64834
Step 78: 64834 + 842 = 65676
Step 79: 65676 + 842 = 66518
Step 80: 66518 + 842 = 67360
Step 81: 67360 + 842 = 68202
Step 82: 68202 + 842 = 69044
Step 83: 69044 + 842 = 69886
Step 84: 69886 + 842 = 70728
Step 85: 70728 + 842 = 71570
Step 86: 71570 + 842 = 72412
Step 87: 72412 + 842 = 73254
Step 88: 73254 + 842 = 74096
Step 89: 74096 + 842 = 74938

So, 842*89 = 74938