OK, let's crack this. We're given 874 and our task is to multiply it by 20. Essentially, we'll be adding 874 to itself 20 times.
Step 1: 0 + 874 = 874
Step 2: 874 + 874 = 1748
Step 3: 1748 + 874 = 2622
Step 4: 2622 + 874 = 3496
Step 5: 3496 + 874 = 4370
Step 6: 4370 + 874 = 5244
Step 7: 5244 + 874 = 6118
Step 8: 6118 + 874 = 6992
Step 9: 6992 + 874 = 7866
Step 10: 7866 + 874 = 8740
Step 11: 8740 + 874 = 9614
Step 12: 9614 + 874 = 10488
Step 13: 10488 + 874 = 11362
Step 14: 11362 + 874 = 12236
Step 15: 12236 + 874 = 13110
Step 16: 13110 + 874 = 13984
Step 17: 13984 + 874 = 14858
Step 18: 14858 + 874 = 15732
Step 19: 15732 + 874 = 16606
Step 20: 16606 + 874 = 17480

So, 874*20 = 17480