Alright, let's solve this math problem step by step. First, we have the number 337. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 21. So, we're going to take the number 337 and add it to itself 21 times.
Step 1: 0 + 337 = 337
Step 2: 337 + 337 = 674
Step 3: 674 + 337 = 1011
Step 4: 1011 + 337 = 1348
Step 5: 1348 + 337 = 1685
Step 6: 1685 + 337 = 2022
Step 7: 2022 + 337 = 2359
Step 8: 2359 + 337 = 2696
Step 9: 2696 + 337 = 3033
Step 10: 3033 + 337 = 3370
Step 11: 3370 + 337 = 3707
Step 12: 3707 + 337 = 4044
Step 13: 4044 + 337 = 4381
Step 14: 4381 + 337 = 4718
Step 15: 4718 + 337 = 5055
Step 16: 5055 + 337 = 5392
Step 17: 5392 + 337 = 5729
Step 18: 5729 + 337 = 6066
Step 19: 6066 + 337 = 6403
Step 20: 6403 + 337 = 6740
Step 21: 6740 + 337 = 7077

So, 337*21 = 7077