Let's get this math done. We have 855 and we're going to multiply it by 4. This is the same as taking 855 and adding it to itself 4 times.
Step 1: 0 + 855 = 855
Step 2: 855 + 855 = 1710
Step 3: 1710 + 855 = 2565
Step 4: 2565 + 855 = 3420

So, 855*4 = 3420