OK, let's crack this. We're given 381 and our task is to multiply it by 15. Essentially, we'll be adding 381 to itself 15 times.
Step 1: 0 + 381 = 381
Step 2: 381 + 381 = 762
Step 3: 762 + 381 = 1143
Step 4: 1143 + 381 = 1524
Step 5: 1524 + 381 = 1905
Step 6: 1905 + 381 = 2286
Step 7: 2286 + 381 = 2667
Step 8: 2667 + 381 = 3048
Step 9: 3048 + 381 = 3429
Step 10: 3429 + 381 = 3810
Step 11: 3810 + 381 = 4191
Step 12: 4191 + 381 = 4572
Step 13: 4572 + 381 = 4953
Step 14: 4953 + 381 = 5334
Step 15: 5334 + 381 = 5715

So, 381*15 = 5715