Without delay, let's solve this. We've got 501 and we will be multiplying it by 31, that is, adding 501 to itself 31 times.
Step 1: 0 + 501 = 501
Step 2: 501 + 501 = 1002
Step 3: 1002 + 501 = 1503
Step 4: 1503 + 501 = 2004
Step 5: 2004 + 501 = 2505
Step 6: 2505 + 501 = 3006
Step 7: 3006 + 501 = 3507
Step 8: 3507 + 501 = 4008
Step 9: 4008 + 501 = 4509
Step 10: 4509 + 501 = 5010
Step 11: 5010 + 501 = 5511
Step 12: 5511 + 501 = 6012
Step 13: 6012 + 501 = 6513
Step 14: 6513 + 501 = 7014
Step 15: 7014 + 501 = 7515
Step 16: 7515 + 501 = 8016
Step 17: 8016 + 501 = 8517
Step 18: 8517 + 501 = 9018
Step 19: 9018 + 501 = 9519
Step 20: 9519 + 501 = 10020
Step 21: 10020 + 501 = 10521
Step 22: 10521 + 501 = 11022
Step 23: 11022 + 501 = 11523
Step 24: 11523 + 501 = 12024
Step 25: 12024 + 501 = 12525
Step 26: 12525 + 501 = 13026
Step 27: 13026 + 501 = 13527
Step 28: 13527 + 501 = 14028
Step 29: 14028 + 501 = 14529
Step 30: 14529 + 501 = 15030
Step 31: 15030 + 501 = 15531

So, 501*31 = 15531