Let's roll up our sleeves and solve this. We have 786 and we're going to multiply it by 39, essentially adding 786 to itself 39 times.
Step 1: 0 + 786 = 786
Step 2: 786 + 786 = 1572
Step 3: 1572 + 786 = 2358
Step 4: 2358 + 786 = 3144
Step 5: 3144 + 786 = 3930
Step 6: 3930 + 786 = 4716
Step 7: 4716 + 786 = 5502
Step 8: 5502 + 786 = 6288
Step 9: 6288 + 786 = 7074
Step 10: 7074 + 786 = 7860
Step 11: 7860 + 786 = 8646
Step 12: 8646 + 786 = 9432
Step 13: 9432 + 786 = 10218
Step 14: 10218 + 786 = 11004
Step 15: 11004 + 786 = 11790
Step 16: 11790 + 786 = 12576
Step 17: 12576 + 786 = 13362
Step 18: 13362 + 786 = 14148
Step 19: 14148 + 786 = 14934
Step 20: 14934 + 786 = 15720
Step 21: 15720 + 786 = 16506
Step 22: 16506 + 786 = 17292
Step 23: 17292 + 786 = 18078
Step 24: 18078 + 786 = 18864
Step 25: 18864 + 786 = 19650
Step 26: 19650 + 786 = 20436
Step 27: 20436 + 786 = 21222
Step 28: 21222 + 786 = 22008
Step 29: 22008 + 786 = 22794
Step 30: 22794 + 786 = 23580
Step 31: 23580 + 786 = 24366
Step 32: 24366 + 786 = 25152
Step 33: 25152 + 786 = 25938
Step 34: 25938 + 786 = 26724
Step 35: 26724 + 786 = 27510
Step 36: 27510 + 786 = 28296
Step 37: 28296 + 786 = 29082
Step 38: 29082 + 786 = 29868
Step 39: 29868 + 786 = 30654

So, 786*39 = 30654