Alright, let's solve this math problem step by step. First, we have the number 165. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 21. So, we're going to take the number 165 and add it to itself 21 times.
Step 1: 0 + 165 = 165
Step 2: 165 + 165 = 330
Step 3: 330 + 165 = 495
Step 4: 495 + 165 = 660
Step 5: 660 + 165 = 825
Step 6: 825 + 165 = 990
Step 7: 990 + 165 = 1155
Step 8: 1155 + 165 = 1320
Step 9: 1320 + 165 = 1485
Step 10: 1485 + 165 = 1650
Step 11: 1650 + 165 = 1815
Step 12: 1815 + 165 = 1980
Step 13: 1980 + 165 = 2145
Step 14: 2145 + 165 = 2310
Step 15: 2310 + 165 = 2475
Step 16: 2475 + 165 = 2640
Step 17: 2640 + 165 = 2805
Step 18: 2805 + 165 = 2970
Step 19: 2970 + 165 = 3135
Step 20: 3135 + 165 = 3300
Step 21: 3300 + 165 = 3465

So, 165*21 = 3465