OK, let's crack this. We're given 390 and our task is to multiply it by 4. Essentially, we'll be adding 390 to itself 4 times.
Step 1: 0 + 390 = 390
Step 2: 390 + 390 = 780
Step 3: 780 + 390 = 1170
Step 4: 1170 + 390 = 1560

So, 390*4 = 1560