OK, let's crack this. We're given 818 and our task is to multiply it by 31. Essentially, we'll be adding 818 to itself 31 times.
Step 1: 0 + 818 = 818
Step 2: 818 + 818 = 1636
Step 3: 1636 + 818 = 2454
Step 4: 2454 + 818 = 3272
Step 5: 3272 + 818 = 4090
Step 6: 4090 + 818 = 4908
Step 7: 4908 + 818 = 5726
Step 8: 5726 + 818 = 6544
Step 9: 6544 + 818 = 7362
Step 10: 7362 + 818 = 8180
Step 11: 8180 + 818 = 8998
Step 12: 8998 + 818 = 9816
Step 13: 9816 + 818 = 10634
Step 14: 10634 + 818 = 11452
Step 15: 11452 + 818 = 12270
Step 16: 12270 + 818 = 13088
Step 17: 13088 + 818 = 13906
Step 18: 13906 + 818 = 14724
Step 19: 14724 + 818 = 15542
Step 20: 15542 + 818 = 16360
Step 21: 16360 + 818 = 17178
Step 22: 17178 + 818 = 17996
Step 23: 17996 + 818 = 18814
Step 24: 18814 + 818 = 19632
Step 25: 19632 + 818 = 20450
Step 26: 20450 + 818 = 21268
Step 27: 21268 + 818 = 22086
Step 28: 22086 + 818 = 22904
Step 29: 22904 + 818 = 23722
Step 30: 23722 + 818 = 24540
Step 31: 24540 + 818 = 25358

So, 818*31 = 25358