Alright, let's solve this math problem step by step. First, we have the number 559. 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 559 and add it to itself 21 times.
Step 1: 0 + 559 = 559
Step 2: 559 + 559 = 1118
Step 3: 1118 + 559 = 1677
Step 4: 1677 + 559 = 2236
Step 5: 2236 + 559 = 2795
Step 6: 2795 + 559 = 3354
Step 7: 3354 + 559 = 3913
Step 8: 3913 + 559 = 4472
Step 9: 4472 + 559 = 5031
Step 10: 5031 + 559 = 5590
Step 11: 5590 + 559 = 6149
Step 12: 6149 + 559 = 6708
Step 13: 6708 + 559 = 7267
Step 14: 7267 + 559 = 7826
Step 15: 7826 + 559 = 8385
Step 16: 8385 + 559 = 8944
Step 17: 8944 + 559 = 9503
Step 18: 9503 + 559 = 10062
Step 19: 10062 + 559 = 10621
Step 20: 10621 + 559 = 11180
Step 21: 11180 + 559 = 11739

So, 559*21 = 11739