Let's get this math done. We have 875 and we're going to multiply it by 20. This is the same as taking 875 and adding it to itself 20 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

So, 875*20 = 17500