Without delay, let's solve this. We've got 709 and we will be multiplying it by 21, that is, adding 709 to itself 21 times.
Step 1: 0 + 709 = 709
Step 2: 709 + 709 = 1418
Step 3: 1418 + 709 = 2127
Step 4: 2127 + 709 = 2836
Step 5: 2836 + 709 = 3545
Step 6: 3545 + 709 = 4254
Step 7: 4254 + 709 = 4963
Step 8: 4963 + 709 = 5672
Step 9: 5672 + 709 = 6381
Step 10: 6381 + 709 = 7090
Step 11: 7090 + 709 = 7799
Step 12: 7799 + 709 = 8508
Step 13: 8508 + 709 = 9217
Step 14: 9217 + 709 = 9926
Step 15: 9926 + 709 = 10635
Step 16: 10635 + 709 = 11344
Step 17: 11344 + 709 = 12053
Step 18: 12053 + 709 = 12762
Step 19: 12762 + 709 = 13471
Step 20: 13471 + 709 = 14180
Step 21: 14180 + 709 = 14889

So, 709*21 = 14889