OK, let's work through this together. We're starting with 875 and we're going to multiply it by 66, which means we add 875 to itself 66 times.
Step 1: 0 + 875 = 875
Step 2: 875 + 875 = 1750
Step 3: 1750 + 875 = 2625
Step 4: 2625 + 875 = 3500
Step 5: 3500 + 875 = 4375
Step 6: 4375 + 875 = 5250
Step 7: 5250 + 875 = 6125
Step 8: 6125 + 875 = 7000
Step 9: 7000 + 875 = 7875
Step 10: 7875 + 875 = 8750
Step 11: 8750 + 875 = 9625
Step 12: 9625 + 875 = 10500
Step 13: 10500 + 875 = 11375
Step 14: 11375 + 875 = 12250
Step 15: 12250 + 875 = 13125
Step 16: 13125 + 875 = 14000
Step 17: 14000 + 875 = 14875
Step 18: 14875 + 875 = 15750
Step 19: 15750 + 875 = 16625
Step 20: 16625 + 875 = 17500
Step 21: 17500 + 875 = 18375
Step 22: 18375 + 875 = 19250
Step 23: 19250 + 875 = 20125
Step 24: 20125 + 875 = 21000
Step 25: 21000 + 875 = 21875
Step 26: 21875 + 875 = 22750
Step 27: 22750 + 875 = 23625
Step 28: 23625 + 875 = 24500
Step 29: 24500 + 875 = 25375
Step 30: 25375 + 875 = 26250
Step 31: 26250 + 875 = 27125
Step 32: 27125 + 875 = 28000
Step 33: 28000 + 875 = 28875
Step 34: 28875 + 875 = 29750
Step 35: 29750 + 875 = 30625
Step 36: 30625 + 875 = 31500
Step 37: 31500 + 875 = 32375
Step 38: 32375 + 875 = 33250
Step 39: 33250 + 875 = 34125
Step 40: 34125 + 875 = 35000
Step 41: 35000 + 875 = 35875
Step 42: 35875 + 875 = 36750
Step 43: 36750 + 875 = 37625
Step 44: 37625 + 875 = 38500
Step 45: 38500 + 875 = 39375
Step 46: 39375 + 875 = 40250
Step 47: 40250 + 875 = 41125
Step 48: 41125 + 875 = 42000
Step 49: 42000 + 875 = 42875
Step 50: 42875 + 875 = 43750
Step 51: 43750 + 875 = 44625
Step 52: 44625 + 875 = 45500
Step 53: 45500 + 875 = 46375
Step 54: 46375 + 875 = 47250
Step 55: 47250 + 875 = 48125
Step 56: 48125 + 875 = 49000
Step 57: 49000 + 875 = 49875
Step 58: 49875 + 875 = 50750
Step 59: 50750 + 875 = 51625
Step 60: 51625 + 875 = 52500
Step 61: 52500 + 875 = 53375
Step 62: 53375 + 875 = 54250
Step 63: 54250 + 875 = 55125
Step 64: 55125 + 875 = 56000
Step 65: 56000 + 875 = 56875
Step 66: 56875 + 875 = 57750

So, 875*66 = 57750