Alright, let's solve this math problem step by step. First, we have the number 642. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 4. So, we're going to take the number 642 and add it to itself 4 times.
Step 1: 0 + 642 = 642
Step 2: 642 + 642 = 1284
Step 3: 1284 + 642 = 1926
Step 4: 1926 + 642 = 2568

So, 642*4 = 2568