Sure thing, let's get straight to it. We start with 902 and we're going to multiply it by 20, which means adding 902 to itself 20 times.
Step 1: 0 + 902 = 902
Step 2: 902 + 902 = 1804
Step 3: 1804 + 902 = 2706
Step 4: 2706 + 902 = 3608
Step 5: 3608 + 902 = 4510
Step 6: 4510 + 902 = 5412
Step 7: 5412 + 902 = 6314
Step 8: 6314 + 902 = 7216
Step 9: 7216 + 902 = 8118
Step 10: 8118 + 902 = 9020
Step 11: 9020 + 902 = 9922
Step 12: 9922 + 902 = 10824
Step 13: 10824 + 902 = 11726
Step 14: 11726 + 902 = 12628
Step 15: 12628 + 902 = 13530
Step 16: 13530 + 902 = 14432
Step 17: 14432 + 902 = 15334
Step 18: 15334 + 902 = 16236
Step 19: 16236 + 902 = 17138
Step 20: 17138 + 902 = 18040

So, 902*20 = 18040