OK, let's crack this. We're given 817 and our task is to multiply it by 31. Essentially, we'll be adding 817 to itself 31 times.
Step 1: 0 + 817 = 817
Step 2: 817 + 817 = 1634
Step 3: 1634 + 817 = 2451
Step 4: 2451 + 817 = 3268
Step 5: 3268 + 817 = 4085
Step 6: 4085 + 817 = 4902
Step 7: 4902 + 817 = 5719
Step 8: 5719 + 817 = 6536
Step 9: 6536 + 817 = 7353
Step 10: 7353 + 817 = 8170
Step 11: 8170 + 817 = 8987
Step 12: 8987 + 817 = 9804
Step 13: 9804 + 817 = 10621
Step 14: 10621 + 817 = 11438
Step 15: 11438 + 817 = 12255
Step 16: 12255 + 817 = 13072
Step 17: 13072 + 817 = 13889
Step 18: 13889 + 817 = 14706
Step 19: 14706 + 817 = 15523
Step 20: 15523 + 817 = 16340
Step 21: 16340 + 817 = 17157
Step 22: 17157 + 817 = 17974
Step 23: 17974 + 817 = 18791
Step 24: 18791 + 817 = 19608
Step 25: 19608 + 817 = 20425
Step 26: 20425 + 817 = 21242
Step 27: 21242 + 817 = 22059
Step 28: 22059 + 817 = 22876
Step 29: 22876 + 817 = 23693
Step 30: 23693 + 817 = 24510
Step 31: 24510 + 817 = 25327

So, 817*31 = 25327