OK, let's work through this together. We're starting with 753 and we're going to multiply it by 28, which means we add 753 to itself 28 times.
Step 1: 0 + 753 = 753
Step 2: 753 + 753 = 1506
Step 3: 1506 + 753 = 2259
Step 4: 2259 + 753 = 3012
Step 5: 3012 + 753 = 3765
Step 6: 3765 + 753 = 4518
Step 7: 4518 + 753 = 5271
Step 8: 5271 + 753 = 6024
Step 9: 6024 + 753 = 6777
Step 10: 6777 + 753 = 7530
Step 11: 7530 + 753 = 8283
Step 12: 8283 + 753 = 9036
Step 13: 9036 + 753 = 9789
Step 14: 9789 + 753 = 10542
Step 15: 10542 + 753 = 11295
Step 16: 11295 + 753 = 12048
Step 17: 12048 + 753 = 12801
Step 18: 12801 + 753 = 13554
Step 19: 13554 + 753 = 14307
Step 20: 14307 + 753 = 15060
Step 21: 15060 + 753 = 15813
Step 22: 15813 + 753 = 16566
Step 23: 16566 + 753 = 17319
Step 24: 17319 + 753 = 18072
Step 25: 18072 + 753 = 18825
Step 26: 18825 + 753 = 19578
Step 27: 19578 + 753 = 20331
Step 28: 20331 + 753 = 21084

So, 753*28 = 21084