OK, let's crack this. We're given 135 and our task is to multiply it by 4. Essentially, we'll be adding 135 to itself 4 times.
Step 1: 0 + 135 = 135
Step 2: 135 + 135 = 270
Step 3: 270 + 135 = 405
Step 4: 405 + 135 = 540

So, 135*4 = 540