OK, let's work through this together. We're starting with 851 and we're going to multiply it by 39, which means we add 851 to itself 39 times.
Step 1: 0 + 851 = 851
Step 2: 851 + 851 = 1702
Step 3: 1702 + 851 = 2553
Step 4: 2553 + 851 = 3404
Step 5: 3404 + 851 = 4255
Step 6: 4255 + 851 = 5106
Step 7: 5106 + 851 = 5957
Step 8: 5957 + 851 = 6808
Step 9: 6808 + 851 = 7659
Step 10: 7659 + 851 = 8510
Step 11: 8510 + 851 = 9361
Step 12: 9361 + 851 = 10212
Step 13: 10212 + 851 = 11063
Step 14: 11063 + 851 = 11914
Step 15: 11914 + 851 = 12765
Step 16: 12765 + 851 = 13616
Step 17: 13616 + 851 = 14467
Step 18: 14467 + 851 = 15318
Step 19: 15318 + 851 = 16169
Step 20: 16169 + 851 = 17020
Step 21: 17020 + 851 = 17871
Step 22: 17871 + 851 = 18722
Step 23: 18722 + 851 = 19573
Step 24: 19573 + 851 = 20424
Step 25: 20424 + 851 = 21275
Step 26: 21275 + 851 = 22126
Step 27: 22126 + 851 = 22977
Step 28: 22977 + 851 = 23828
Step 29: 23828 + 851 = 24679
Step 30: 24679 + 851 = 25530
Step 31: 25530 + 851 = 26381
Step 32: 26381 + 851 = 27232
Step 33: 27232 + 851 = 28083
Step 34: 28083 + 851 = 28934
Step 35: 28934 + 851 = 29785
Step 36: 29785 + 851 = 30636
Step 37: 30636 + 851 = 31487
Step 38: 31487 + 851 = 32338
Step 39: 32338 + 851 = 33189

So, 851*39 = 33189