Alright, let's solve this math problem step by step. First, we have the number 999. 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 999 and add it to itself 25 times.
Step 1: 0 + 999 = 999
Step 2: 999 + 999 = 1998
Step 3: 1998 + 999 = 2997
Step 4: 2997 + 999 = 3996
Step 5: 3996 + 999 = 4995
Step 6: 4995 + 999 = 5994
Step 7: 5994 + 999 = 6993
Step 8: 6993 + 999 = 7992
Step 9: 7992 + 999 = 8991
Step 10: 8991 + 999 = 9990
Step 11: 9990 + 999 = 10989
Step 12: 10989 + 999 = 11988
Step 13: 11988 + 999 = 12987
Step 14: 12987 + 999 = 13986
Step 15: 13986 + 999 = 14985
Step 16: 14985 + 999 = 15984
Step 17: 15984 + 999 = 16983
Step 18: 16983 + 999 = 17982
Step 19: 17982 + 999 = 18981
Step 20: 18981 + 999 = 19980
Step 21: 19980 + 999 = 20979
Step 22: 20979 + 999 = 21978
Step 23: 21978 + 999 = 22977
Step 24: 22977 + 999 = 23976
Step 25: 23976 + 999 = 24975

So, 999*25 = 24975