Sure thing! We've got 820 and we're gonna multiply it by 39. That's the same as adding 820 to itself 39 times.
Step 1: 0 + 820 = 820
Step 2: 820 + 820 = 1640
Step 3: 1640 + 820 = 2460
Step 4: 2460 + 820 = 3280
Step 5: 3280 + 820 = 4100
Step 6: 4100 + 820 = 4920
Step 7: 4920 + 820 = 5740
Step 8: 5740 + 820 = 6560
Step 9: 6560 + 820 = 7380
Step 10: 7380 + 820 = 8200
Step 11: 8200 + 820 = 9020
Step 12: 9020 + 820 = 9840
Step 13: 9840 + 820 = 10660
Step 14: 10660 + 820 = 11480
Step 15: 11480 + 820 = 12300
Step 16: 12300 + 820 = 13120
Step 17: 13120 + 820 = 13940
Step 18: 13940 + 820 = 14760
Step 19: 14760 + 820 = 15580
Step 20: 15580 + 820 = 16400
Step 21: 16400 + 820 = 17220
Step 22: 17220 + 820 = 18040
Step 23: 18040 + 820 = 18860
Step 24: 18860 + 820 = 19680
Step 25: 19680 + 820 = 20500
Step 26: 20500 + 820 = 21320
Step 27: 21320 + 820 = 22140
Step 28: 22140 + 820 = 22960
Step 29: 22960 + 820 = 23780
Step 30: 23780 + 820 = 24600
Step 31: 24600 + 820 = 25420
Step 32: 25420 + 820 = 26240
Step 33: 26240 + 820 = 27060
Step 34: 27060 + 820 = 27880
Step 35: 27880 + 820 = 28700
Step 36: 28700 + 820 = 29520
Step 37: 29520 + 820 = 30340
Step 38: 30340 + 820 = 31160
Step 39: 31160 + 820 = 31980

So, 820*39 = 31980