OK, let's crack this. We're given 852 and our task is to multiply it by 31. Essentially, we'll be adding 852 to itself 31 times.
Step 1: 0 + 852 = 852
Step 2: 852 + 852 = 1704
Step 3: 1704 + 852 = 2556
Step 4: 2556 + 852 = 3408
Step 5: 3408 + 852 = 4260
Step 6: 4260 + 852 = 5112
Step 7: 5112 + 852 = 5964
Step 8: 5964 + 852 = 6816
Step 9: 6816 + 852 = 7668
Step 10: 7668 + 852 = 8520
Step 11: 8520 + 852 = 9372
Step 12: 9372 + 852 = 10224
Step 13: 10224 + 852 = 11076
Step 14: 11076 + 852 = 11928
Step 15: 11928 + 852 = 12780
Step 16: 12780 + 852 = 13632
Step 17: 13632 + 852 = 14484
Step 18: 14484 + 852 = 15336
Step 19: 15336 + 852 = 16188
Step 20: 16188 + 852 = 17040
Step 21: 17040 + 852 = 17892
Step 22: 17892 + 852 = 18744
Step 23: 18744 + 852 = 19596
Step 24: 19596 + 852 = 20448
Step 25: 20448 + 852 = 21300
Step 26: 21300 + 852 = 22152
Step 27: 22152 + 852 = 23004
Step 28: 23004 + 852 = 23856
Step 29: 23856 + 852 = 24708
Step 30: 24708 + 852 = 25560
Step 31: 25560 + 852 = 26412

So, 852*31 = 26412