Let's get this math done. We have 939 and we're going to multiply it by 30. This is the same as taking 939 and adding it to itself 30 times.
Step 1: 0 + 939 = 939
Step 2: 939 + 939 = 1878
Step 3: 1878 + 939 = 2817
Step 4: 2817 + 939 = 3756
Step 5: 3756 + 939 = 4695
Step 6: 4695 + 939 = 5634
Step 7: 5634 + 939 = 6573
Step 8: 6573 + 939 = 7512
Step 9: 7512 + 939 = 8451
Step 10: 8451 + 939 = 9390
Step 11: 9390 + 939 = 10329
Step 12: 10329 + 939 = 11268
Step 13: 11268 + 939 = 12207
Step 14: 12207 + 939 = 13146
Step 15: 13146 + 939 = 14085
Step 16: 14085 + 939 = 15024
Step 17: 15024 + 939 = 15963
Step 18: 15963 + 939 = 16902
Step 19: 16902 + 939 = 17841
Step 20: 17841 + 939 = 18780
Step 21: 18780 + 939 = 19719
Step 22: 19719 + 939 = 20658
Step 23: 20658 + 939 = 21597
Step 24: 21597 + 939 = 22536
Step 25: 22536 + 939 = 23475
Step 26: 23475 + 939 = 24414
Step 27: 24414 + 939 = 25353
Step 28: 25353 + 939 = 26292
Step 29: 26292 + 939 = 27231
Step 30: 27231 + 939 = 28170

So, 939*30 = 28170