OK, let's crack this. We're given 673 and our task is to multiply it by 25. Essentially, we'll be adding 673 to itself 25 times.
Step 1: 0 + 673 = 673
Step 2: 673 + 673 = 1346
Step 3: 1346 + 673 = 2019
Step 4: 2019 + 673 = 2692
Step 5: 2692 + 673 = 3365
Step 6: 3365 + 673 = 4038
Step 7: 4038 + 673 = 4711
Step 8: 4711 + 673 = 5384
Step 9: 5384 + 673 = 6057
Step 10: 6057 + 673 = 6730
Step 11: 6730 + 673 = 7403
Step 12: 7403 + 673 = 8076
Step 13: 8076 + 673 = 8749
Step 14: 8749 + 673 = 9422
Step 15: 9422 + 673 = 10095
Step 16: 10095 + 673 = 10768
Step 17: 10768 + 673 = 11441
Step 18: 11441 + 673 = 12114
Step 19: 12114 + 673 = 12787
Step 20: 12787 + 673 = 13460
Step 21: 13460 + 673 = 14133
Step 22: 14133 + 673 = 14806
Step 23: 14806 + 673 = 15479
Step 24: 15479 + 673 = 16152
Step 25: 16152 + 673 = 16825

So, 673*25 = 16825