OK, let's work through this together. We're starting with 8 and we're going to multiply it by 84, which means we add 8 to itself 84 times.
Step 1: 0 + 8 = 8
Step 2: 8 + 8 = 16
Step 3: 16 + 8 = 24
Step 4: 24 + 8 = 32
Step 5: 32 + 8 = 40
Step 6: 40 + 8 = 48
Step 7: 48 + 8 = 56
Step 8: 56 + 8 = 64
Step 9: 64 + 8 = 72
Step 10: 72 + 8 = 80
Step 11: 80 + 8 = 88
Step 12: 88 + 8 = 96
Step 13: 96 + 8 = 104
Step 14: 104 + 8 = 112
Step 15: 112 + 8 = 120
Step 16: 120 + 8 = 128
Step 17: 128 + 8 = 136
Step 18: 136 + 8 = 144
Step 19: 144 + 8 = 152
Step 20: 152 + 8 = 160
Step 21: 160 + 8 = 168
Step 22: 168 + 8 = 176
Step 23: 176 + 8 = 184
Step 24: 184 + 8 = 192
Step 25: 192 + 8 = 200
Step 26: 200 + 8 = 208
Step 27: 208 + 8 = 216
Step 28: 216 + 8 = 224
Step 29: 224 + 8 = 232
Step 30: 232 + 8 = 240
Step 31: 240 + 8 = 248
Step 32: 248 + 8 = 256
Step 33: 256 + 8 = 264
Step 34: 264 + 8 = 272
Step 35: 272 + 8 = 280
Step 36: 280 + 8 = 288
Step 37: 288 + 8 = 296
Step 38: 296 + 8 = 304
Step 39: 304 + 8 = 312
Step 40: 312 + 8 = 320
Step 41: 320 + 8 = 328
Step 42: 328 + 8 = 336
Step 43: 336 + 8 = 344
Step 44: 344 + 8 = 352
Step 45: 352 + 8 = 360
Step 46: 360 + 8 = 368
Step 47: 368 + 8 = 376
Step 48: 376 + 8 = 384
Step 49: 384 + 8 = 392
Step 50: 392 + 8 = 400
Step 51: 400 + 8 = 408
Step 52: 408 + 8 = 416
Step 53: 416 + 8 = 424
Step 54: 424 + 8 = 432
Step 55: 432 + 8 = 440
Step 56: 440 + 8 = 448
Step 57: 448 + 8 = 456
Step 58: 456 + 8 = 464
Step 59: 464 + 8 = 472
Step 60: 472 + 8 = 480
Step 61: 480 + 8 = 488
Step 62: 488 + 8 = 496
Step 63: 496 + 8 = 504
Step 64: 504 + 8 = 512
Step 65: 512 + 8 = 520
Step 66: 520 + 8 = 528
Step 67: 528 + 8 = 536
Step 68: 536 + 8 = 544
Step 69: 544 + 8 = 552
Step 70: 552 + 8 = 560
Step 71: 560 + 8 = 568
Step 72: 568 + 8 = 576
Step 73: 576 + 8 = 584
Step 74: 584 + 8 = 592
Step 75: 592 + 8 = 600
Step 76: 600 + 8 = 608
Step 77: 608 + 8 = 616
Step 78: 616 + 8 = 624
Step 79: 624 + 8 = 632
Step 80: 632 + 8 = 640
Step 81: 640 + 8 = 648
Step 82: 648 + 8 = 656
Step 83: 656 + 8 = 664
Step 84: 664 + 8 = 672

So, 8*84 = 672