Let's get this math done. We have 421 and we're going to multiply it by 3. This is the same as taking 421 and adding it to itself 3 times.
Step 1: 0 + 421 = 421
Step 2: 421 + 421 = 842
Step 3: 842 + 421 = 1263

So, 421*3 = 1263