Alright, let's solve this math problem step by step. First, we have the number 643. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 55. So, we're going to take the number 643 and add it to itself 55 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

So, 643*55 = 35365