Sure thing! We've got 39 and we're gonna multiply it by 20. That's the same as adding 39 to itself 20 times.
Step 1: 0 + 39 = 39
Step 2: 39 + 39 = 78
Step 3: 78 + 39 = 117
Step 4: 117 + 39 = 156
Step 5: 156 + 39 = 195
Step 6: 195 + 39 = 234
Step 7: 234 + 39 = 273
Step 8: 273 + 39 = 312
Step 9: 312 + 39 = 351
Step 10: 351 + 39 = 390
Step 11: 390 + 39 = 429
Step 12: 429 + 39 = 468
Step 13: 468 + 39 = 507
Step 14: 507 + 39 = 546
Step 15: 546 + 39 = 585
Step 16: 585 + 39 = 624
Step 17: 624 + 39 = 663
Step 18: 663 + 39 = 702
Step 19: 702 + 39 = 741
Step 20: 741 + 39 = 780

So, 39*20 = 780