Without delay, let's solve this. We've got 710 and we will be multiplying it by 21, that is, adding 710 to itself 21 times.
Step 1: 0 + 710 = 710
Step 2: 710 + 710 = 1420
Step 3: 1420 + 710 = 2130
Step 4: 2130 + 710 = 2840
Step 5: 2840 + 710 = 3550
Step 6: 3550 + 710 = 4260
Step 7: 4260 + 710 = 4970
Step 8: 4970 + 710 = 5680
Step 9: 5680 + 710 = 6390
Step 10: 6390 + 710 = 7100
Step 11: 7100 + 710 = 7810
Step 12: 7810 + 710 = 8520
Step 13: 8520 + 710 = 9230
Step 14: 9230 + 710 = 9940
Step 15: 9940 + 710 = 10650
Step 16: 10650 + 710 = 11360
Step 17: 11360 + 710 = 12070
Step 18: 12070 + 710 = 12780
Step 19: 12780 + 710 = 13490
Step 20: 13490 + 710 = 14200
Step 21: 14200 + 710 = 14910

So, 710*21 = 14910