Alright, let's solve this math problem step by step. First, we have the number 645. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 22. So, we're going to take the number 645 and add it to itself 22 times.
Step 1: 0 + 645 = 645
Step 2: 645 + 645 = 1290
Step 3: 1290 + 645 = 1935
Step 4: 1935 + 645 = 2580
Step 5: 2580 + 645 = 3225
Step 6: 3225 + 645 = 3870
Step 7: 3870 + 645 = 4515
Step 8: 4515 + 645 = 5160
Step 9: 5160 + 645 = 5805
Step 10: 5805 + 645 = 6450
Step 11: 6450 + 645 = 7095
Step 12: 7095 + 645 = 7740
Step 13: 7740 + 645 = 8385
Step 14: 8385 + 645 = 9030
Step 15: 9030 + 645 = 9675
Step 16: 9675 + 645 = 10320
Step 17: 10320 + 645 = 10965
Step 18: 10965 + 645 = 11610
Step 19: 11610 + 645 = 12255
Step 20: 12255 + 645 = 12900
Step 21: 12900 + 645 = 13545
Step 22: 13545 + 645 = 14190

So, 645*22 = 14190