Let's roll up our sleeves and solve this. We have 857 and we're going to multiply it by 29, essentially adding 857 to itself 29 times.
Step 1: 0 + 857 = 857
Step 2: 857 + 857 = 1714
Step 3: 1714 + 857 = 2571
Step 4: 2571 + 857 = 3428
Step 5: 3428 + 857 = 4285
Step 6: 4285 + 857 = 5142
Step 7: 5142 + 857 = 5999
Step 8: 5999 + 857 = 6856
Step 9: 6856 + 857 = 7713
Step 10: 7713 + 857 = 8570
Step 11: 8570 + 857 = 9427
Step 12: 9427 + 857 = 10284
Step 13: 10284 + 857 = 11141
Step 14: 11141 + 857 = 11998
Step 15: 11998 + 857 = 12855
Step 16: 12855 + 857 = 13712
Step 17: 13712 + 857 = 14569
Step 18: 14569 + 857 = 15426
Step 19: 15426 + 857 = 16283
Step 20: 16283 + 857 = 17140
Step 21: 17140 + 857 = 17997
Step 22: 17997 + 857 = 18854
Step 23: 18854 + 857 = 19711
Step 24: 19711 + 857 = 20568
Step 25: 20568 + 857 = 21425
Step 26: 21425 + 857 = 22282
Step 27: 22282 + 857 = 23139
Step 28: 23139 + 857 = 23996
Step 29: 23996 + 857 = 24853

So, 857*29 = 24853