Sure thing! We've got 371 and we're gonna multiply it by 21. That's the same as adding 371 to itself 21 times.
Step 1: 0 + 371 = 371
Step 2: 371 + 371 = 742
Step 3: 742 + 371 = 1113
Step 4: 1113 + 371 = 1484
Step 5: 1484 + 371 = 1855
Step 6: 1855 + 371 = 2226
Step 7: 2226 + 371 = 2597
Step 8: 2597 + 371 = 2968
Step 9: 2968 + 371 = 3339
Step 10: 3339 + 371 = 3710
Step 11: 3710 + 371 = 4081
Step 12: 4081 + 371 = 4452
Step 13: 4452 + 371 = 4823
Step 14: 4823 + 371 = 5194
Step 15: 5194 + 371 = 5565
Step 16: 5565 + 371 = 5936
Step 17: 5936 + 371 = 6307
Step 18: 6307 + 371 = 6678
Step 19: 6678 + 371 = 7049
Step 20: 7049 + 371 = 7420
Step 21: 7420 + 371 = 7791

So, 371*21 = 7791