OK, let's crack this. We're given 359 and our task is to multiply it by 21. Essentially, we'll be adding 359 to itself 21 times.
Step 1: 0 + 359 = 359
Step 2: 359 + 359 = 718
Step 3: 718 + 359 = 1077
Step 4: 1077 + 359 = 1436
Step 5: 1436 + 359 = 1795
Step 6: 1795 + 359 = 2154
Step 7: 2154 + 359 = 2513
Step 8: 2513 + 359 = 2872
Step 9: 2872 + 359 = 3231
Step 10: 3231 + 359 = 3590
Step 11: 3590 + 359 = 3949
Step 12: 3949 + 359 = 4308
Step 13: 4308 + 359 = 4667
Step 14: 4667 + 359 = 5026
Step 15: 5026 + 359 = 5385
Step 16: 5385 + 359 = 5744
Step 17: 5744 + 359 = 6103
Step 18: 6103 + 359 = 6462
Step 19: 6462 + 359 = 6821
Step 20: 6821 + 359 = 7180
Step 21: 7180 + 359 = 7539

So, 359*21 = 7539