Alright, let's solve this math problem step by step. First, we have the number 736. 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 736 and add it to itself 21 times.
Step 1: 0 + 736 = 736
Step 2: 736 + 736 = 1472
Step 3: 1472 + 736 = 2208
Step 4: 2208 + 736 = 2944
Step 5: 2944 + 736 = 3680
Step 6: 3680 + 736 = 4416
Step 7: 4416 + 736 = 5152
Step 8: 5152 + 736 = 5888
Step 9: 5888 + 736 = 6624
Step 10: 6624 + 736 = 7360
Step 11: 7360 + 736 = 8096
Step 12: 8096 + 736 = 8832
Step 13: 8832 + 736 = 9568
Step 14: 9568 + 736 = 10304
Step 15: 10304 + 736 = 11040
Step 16: 11040 + 736 = 11776
Step 17: 11776 + 736 = 12512
Step 18: 12512 + 736 = 13248
Step 19: 13248 + 736 = 13984
Step 20: 13984 + 736 = 14720
Step 21: 14720 + 736 = 15456

So, 736*21 = 15456