OK, let's crack this. We're given 486 and our task is to multiply it by 25. Essentially, we'll be adding 486 to itself 25 times.
Step 1: 0 + 486 = 486
Step 2: 486 + 486 = 972
Step 3: 972 + 486 = 1458
Step 4: 1458 + 486 = 1944
Step 5: 1944 + 486 = 2430
Step 6: 2430 + 486 = 2916
Step 7: 2916 + 486 = 3402
Step 8: 3402 + 486 = 3888
Step 9: 3888 + 486 = 4374
Step 10: 4374 + 486 = 4860
Step 11: 4860 + 486 = 5346
Step 12: 5346 + 486 = 5832
Step 13: 5832 + 486 = 6318
Step 14: 6318 + 486 = 6804
Step 15: 6804 + 486 = 7290
Step 16: 7290 + 486 = 7776
Step 17: 7776 + 486 = 8262
Step 18: 8262 + 486 = 8748
Step 19: 8748 + 486 = 9234
Step 20: 9234 + 486 = 9720
Step 21: 9720 + 486 = 10206
Step 22: 10206 + 486 = 10692
Step 23: 10692 + 486 = 11178
Step 24: 11178 + 486 = 11664
Step 25: 11664 + 486 = 12150

So, 486*25 = 12150