Let's roll up our sleeves and solve this. We have 431 and we're going to multiply it by 29, essentially adding 431 to itself 29 times.
Step 1: 0 + 431 = 431
Step 2: 431 + 431 = 862
Step 3: 862 + 431 = 1293
Step 4: 1293 + 431 = 1724
Step 5: 1724 + 431 = 2155
Step 6: 2155 + 431 = 2586
Step 7: 2586 + 431 = 3017
Step 8: 3017 + 431 = 3448
Step 9: 3448 + 431 = 3879
Step 10: 3879 + 431 = 4310
Step 11: 4310 + 431 = 4741
Step 12: 4741 + 431 = 5172
Step 13: 5172 + 431 = 5603
Step 14: 5603 + 431 = 6034
Step 15: 6034 + 431 = 6465
Step 16: 6465 + 431 = 6896
Step 17: 6896 + 431 = 7327
Step 18: 7327 + 431 = 7758
Step 19: 7758 + 431 = 8189
Step 20: 8189 + 431 = 8620
Step 21: 8620 + 431 = 9051
Step 22: 9051 + 431 = 9482
Step 23: 9482 + 431 = 9913
Step 24: 9913 + 431 = 10344
Step 25: 10344 + 431 = 10775
Step 26: 10775 + 431 = 11206
Step 27: 11206 + 431 = 11637
Step 28: 11637 + 431 = 12068
Step 29: 12068 + 431 = 12499

So, 431*29 = 12499