Alright, let's solve this math problem step by step. First, we have the number 81. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 31. So, we're going to take the number 81 and add it to itself 31 times.
Step 1: 0 + 81 = 81
Step 2: 81 + 81 = 162
Step 3: 162 + 81 = 243
Step 4: 243 + 81 = 324
Step 5: 324 + 81 = 405
Step 6: 405 + 81 = 486
Step 7: 486 + 81 = 567
Step 8: 567 + 81 = 648
Step 9: 648 + 81 = 729
Step 10: 729 + 81 = 810
Step 11: 810 + 81 = 891
Step 12: 891 + 81 = 972
Step 13: 972 + 81 = 1053
Step 14: 1053 + 81 = 1134
Step 15: 1134 + 81 = 1215
Step 16: 1215 + 81 = 1296
Step 17: 1296 + 81 = 1377
Step 18: 1377 + 81 = 1458
Step 19: 1458 + 81 = 1539
Step 20: 1539 + 81 = 1620
Step 21: 1620 + 81 = 1701
Step 22: 1701 + 81 = 1782
Step 23: 1782 + 81 = 1863
Step 24: 1863 + 81 = 1944
Step 25: 1944 + 81 = 2025
Step 26: 2025 + 81 = 2106
Step 27: 2106 + 81 = 2187
Step 28: 2187 + 81 = 2268
Step 29: 2268 + 81 = 2349
Step 30: 2349 + 81 = 2430
Step 31: 2430 + 81 = 2511

So, 81*31 = 2511