OK, let's work through this together. We're starting with 721 and we're going to multiply it by 24, which means we add 721 to itself 24 times.
Step 1: 0 + 721 = 721
Step 2: 721 + 721 = 1442
Step 3: 1442 + 721 = 2163
Step 4: 2163 + 721 = 2884
Step 5: 2884 + 721 = 3605
Step 6: 3605 + 721 = 4326
Step 7: 4326 + 721 = 5047
Step 8: 5047 + 721 = 5768
Step 9: 5768 + 721 = 6489
Step 10: 6489 + 721 = 7210
Step 11: 7210 + 721 = 7931
Step 12: 7931 + 721 = 8652
Step 13: 8652 + 721 = 9373
Step 14: 9373 + 721 = 10094
Step 15: 10094 + 721 = 10815
Step 16: 10815 + 721 = 11536
Step 17: 11536 + 721 = 12257
Step 18: 12257 + 721 = 12978
Step 19: 12978 + 721 = 13699
Step 20: 13699 + 721 = 14420
Step 21: 14420 + 721 = 15141
Step 22: 15141 + 721 = 15862
Step 23: 15862 + 721 = 16583
Step 24: 16583 + 721 = 17304

So, 721*24 = 17304