Alright, let's solve this math problem step by step. First, we have the number 321. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 20. So, we're going to take the number 321 and add it to itself 20 times.
Step 1: 0 + 321 = 321
Step 2: 321 + 321 = 642
Step 3: 642 + 321 = 963
Step 4: 963 + 321 = 1284
Step 5: 1284 + 321 = 1605
Step 6: 1605 + 321 = 1926
Step 7: 1926 + 321 = 2247
Step 8: 2247 + 321 = 2568
Step 9: 2568 + 321 = 2889
Step 10: 2889 + 321 = 3210
Step 11: 3210 + 321 = 3531
Step 12: 3531 + 321 = 3852
Step 13: 3852 + 321 = 4173
Step 14: 4173 + 321 = 4494
Step 15: 4494 + 321 = 4815
Step 16: 4815 + 321 = 5136
Step 17: 5136 + 321 = 5457
Step 18: 5457 + 321 = 5778
Step 19: 5778 + 321 = 6099
Step 20: 6099 + 321 = 6420

So, 321*20 = 6420