Alright, let's solve this math problem step by step. First, we have the number 846. 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 846 and add it to itself 21 times.
Step 1: 0 + 846 = 846
Step 2: 846 + 846 = 1692
Step 3: 1692 + 846 = 2538
Step 4: 2538 + 846 = 3384
Step 5: 3384 + 846 = 4230
Step 6: 4230 + 846 = 5076
Step 7: 5076 + 846 = 5922
Step 8: 5922 + 846 = 6768
Step 9: 6768 + 846 = 7614
Step 10: 7614 + 846 = 8460
Step 11: 8460 + 846 = 9306
Step 12: 9306 + 846 = 10152
Step 13: 10152 + 846 = 10998
Step 14: 10998 + 846 = 11844
Step 15: 11844 + 846 = 12690
Step 16: 12690 + 846 = 13536
Step 17: 13536 + 846 = 14382
Step 18: 14382 + 846 = 15228
Step 19: 15228 + 846 = 16074
Step 20: 16074 + 846 = 16920
Step 21: 16920 + 846 = 17766

So, 846*21 = 17766