Alright, let's solve this math problem step by step. First, we have the number 661. 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 661 and add it to itself 25 times.
Step 1: 0 + 661 = 661
Step 2: 661 + 661 = 1322
Step 3: 1322 + 661 = 1983
Step 4: 1983 + 661 = 2644
Step 5: 2644 + 661 = 3305
Step 6: 3305 + 661 = 3966
Step 7: 3966 + 661 = 4627
Step 8: 4627 + 661 = 5288
Step 9: 5288 + 661 = 5949
Step 10: 5949 + 661 = 6610
Step 11: 6610 + 661 = 7271
Step 12: 7271 + 661 = 7932
Step 13: 7932 + 661 = 8593
Step 14: 8593 + 661 = 9254
Step 15: 9254 + 661 = 9915
Step 16: 9915 + 661 = 10576
Step 17: 10576 + 661 = 11237
Step 18: 11237 + 661 = 11898
Step 19: 11898 + 661 = 12559
Step 20: 12559 + 661 = 13220
Step 21: 13220 + 661 = 13881
Step 22: 13881 + 661 = 14542
Step 23: 14542 + 661 = 15203
Step 24: 15203 + 661 = 15864
Step 25: 15864 + 661 = 16525

So, 661*25 = 16525