Let's get this math done. We have 266 and we're going to multiply it by 21. This is the same as taking 266 and adding it to itself 21 times.
Step 1: 0 + 266 = 266
Step 2: 266 + 266 = 532
Step 3: 532 + 266 = 798
Step 4: 798 + 266 = 1064
Step 5: 1064 + 266 = 1330
Step 6: 1330 + 266 = 1596
Step 7: 1596 + 266 = 1862
Step 8: 1862 + 266 = 2128
Step 9: 2128 + 266 = 2394
Step 10: 2394 + 266 = 2660
Step 11: 2660 + 266 = 2926
Step 12: 2926 + 266 = 3192
Step 13: 3192 + 266 = 3458
Step 14: 3458 + 266 = 3724
Step 15: 3724 + 266 = 3990
Step 16: 3990 + 266 = 4256
Step 17: 4256 + 266 = 4522
Step 18: 4522 + 266 = 4788
Step 19: 4788 + 266 = 5054
Step 20: 5054 + 266 = 5320
Step 21: 5320 + 266 = 5586

So, 266*21 = 5586