Without delay, let's solve this. We've got 268 and we will be multiplying it by 21, that is, adding 268 to itself 21 times.
Step 1: 0 + 268 = 268
Step 2: 268 + 268 = 536
Step 3: 536 + 268 = 804
Step 4: 804 + 268 = 1072
Step 5: 1072 + 268 = 1340
Step 6: 1340 + 268 = 1608
Step 7: 1608 + 268 = 1876
Step 8: 1876 + 268 = 2144
Step 9: 2144 + 268 = 2412
Step 10: 2412 + 268 = 2680
Step 11: 2680 + 268 = 2948
Step 12: 2948 + 268 = 3216
Step 13: 3216 + 268 = 3484
Step 14: 3484 + 268 = 3752
Step 15: 3752 + 268 = 4020
Step 16: 4020 + 268 = 4288
Step 17: 4288 + 268 = 4556
Step 18: 4556 + 268 = 4824
Step 19: 4824 + 268 = 5092
Step 20: 5092 + 268 = 5360
Step 21: 5360 + 268 = 5628

So, 268*21 = 5628