Alright, let's solve this math problem step by step. First, we have the number 861. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 25. So, we're going to take the number 861 and add it to itself 25 times.
Step 1: 0 + 861 = 861
Step 2: 861 + 861 = 1722
Step 3: 1722 + 861 = 2583
Step 4: 2583 + 861 = 3444
Step 5: 3444 + 861 = 4305
Step 6: 4305 + 861 = 5166
Step 7: 5166 + 861 = 6027
Step 8: 6027 + 861 = 6888
Step 9: 6888 + 861 = 7749
Step 10: 7749 + 861 = 8610
Step 11: 8610 + 861 = 9471
Step 12: 9471 + 861 = 10332
Step 13: 10332 + 861 = 11193
Step 14: 11193 + 861 = 12054
Step 15: 12054 + 861 = 12915
Step 16: 12915 + 861 = 13776
Step 17: 13776 + 861 = 14637
Step 18: 14637 + 861 = 15498
Step 19: 15498 + 861 = 16359
Step 20: 16359 + 861 = 17220
Step 21: 17220 + 861 = 18081
Step 22: 18081 + 861 = 18942
Step 23: 18942 + 861 = 19803
Step 24: 19803 + 861 = 20664
Step 25: 20664 + 861 = 21525

So, 861*25 = 21525