Let's roll up our sleeves and solve this. We have 837 and we're going to multiply it by 13, essentially adding 837 to itself 13 times.
Step 1: 0 + 837 = 837
Step 2: 837 + 837 = 1674
Step 3: 1674 + 837 = 2511
Step 4: 2511 + 837 = 3348
Step 5: 3348 + 837 = 4185
Step 6: 4185 + 837 = 5022
Step 7: 5022 + 837 = 5859
Step 8: 5859 + 837 = 6696
Step 9: 6696 + 837 = 7533
Step 10: 7533 + 837 = 8370
Step 11: 8370 + 837 = 9207
Step 12: 9207 + 837 = 10044
Step 13: 10044 + 837 = 10881

So, 837*13 = 10881