OK, let's crack this. We're given 345 and our task is to multiply it by 4. Essentially, we'll be adding 345 to itself 4 times.
Step 1: 0 + 345 = 345
Step 2: 345 + 345 = 690
Step 3: 690 + 345 = 1035
Step 4: 1035 + 345 = 1380

So, 345*4 = 1380