Sure thing, let's get straight to it. We start with 643 and we're going to multiply it by 68, which means adding 643 to itself 68 times.
Step 1: 0 + 643 = 643
Step 2: 643 + 643 = 1286
Step 3: 1286 + 643 = 1929
Step 4: 1929 + 643 = 2572
Step 5: 2572 + 643 = 3215
Step 6: 3215 + 643 = 3858
Step 7: 3858 + 643 = 4501
Step 8: 4501 + 643 = 5144
Step 9: 5144 + 643 = 5787
Step 10: 5787 + 643 = 6430
Step 11: 6430 + 643 = 7073
Step 12: 7073 + 643 = 7716
Step 13: 7716 + 643 = 8359
Step 14: 8359 + 643 = 9002
Step 15: 9002 + 643 = 9645
Step 16: 9645 + 643 = 10288
Step 17: 10288 + 643 = 10931
Step 18: 10931 + 643 = 11574
Step 19: 11574 + 643 = 12217
Step 20: 12217 + 643 = 12860
Step 21: 12860 + 643 = 13503
Step 22: 13503 + 643 = 14146
Step 23: 14146 + 643 = 14789
Step 24: 14789 + 643 = 15432
Step 25: 15432 + 643 = 16075
Step 26: 16075 + 643 = 16718
Step 27: 16718 + 643 = 17361
Step 28: 17361 + 643 = 18004
Step 29: 18004 + 643 = 18647
Step 30: 18647 + 643 = 19290
Step 31: 19290 + 643 = 19933
Step 32: 19933 + 643 = 20576
Step 33: 20576 + 643 = 21219
Step 34: 21219 + 643 = 21862
Step 35: 21862 + 643 = 22505
Step 36: 22505 + 643 = 23148
Step 37: 23148 + 643 = 23791
Step 38: 23791 + 643 = 24434
Step 39: 24434 + 643 = 25077
Step 40: 25077 + 643 = 25720
Step 41: 25720 + 643 = 26363
Step 42: 26363 + 643 = 27006
Step 43: 27006 + 643 = 27649
Step 44: 27649 + 643 = 28292
Step 45: 28292 + 643 = 28935
Step 46: 28935 + 643 = 29578
Step 47: 29578 + 643 = 30221
Step 48: 30221 + 643 = 30864
Step 49: 30864 + 643 = 31507
Step 50: 31507 + 643 = 32150
Step 51: 32150 + 643 = 32793
Step 52: 32793 + 643 = 33436
Step 53: 33436 + 643 = 34079
Step 54: 34079 + 643 = 34722
Step 55: 34722 + 643 = 35365
Step 56: 35365 + 643 = 36008
Step 57: 36008 + 643 = 36651
Step 58: 36651 + 643 = 37294
Step 59: 37294 + 643 = 37937
Step 60: 37937 + 643 = 38580
Step 61: 38580 + 643 = 39223
Step 62: 39223 + 643 = 39866
Step 63: 39866 + 643 = 40509
Step 64: 40509 + 643 = 41152
Step 65: 41152 + 643 = 41795
Step 66: 41795 + 643 = 42438
Step 67: 42438 + 643 = 43081
Step 68: 43081 + 643 = 43724

So, 643*68 = 43724