OK, let's crack this. We're given 339 and our task is to multiply it by 12. Essentially, we'll be adding 339 to itself 12 times.
Step 1: 0 + 339 = 339
Step 2: 339 + 339 = 678
Step 3: 678 + 339 = 1017
Step 4: 1017 + 339 = 1356
Step 5: 1356 + 339 = 1695
Step 6: 1695 + 339 = 2034
Step 7: 2034 + 339 = 2373
Step 8: 2373 + 339 = 2712
Step 9: 2712 + 339 = 3051
Step 10: 3051 + 339 = 3390
Step 11: 3390 + 339 = 3729
Step 12: 3729 + 339 = 4068

So, 339*12 = 4068