Alright, let's solve this math problem step by step. First, we have the number 879. 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 879 and add it to itself 25 times.
Step 1: 0 + 879 = 879
Step 2: 879 + 879 = 1758
Step 3: 1758 + 879 = 2637
Step 4: 2637 + 879 = 3516
Step 5: 3516 + 879 = 4395
Step 6: 4395 + 879 = 5274
Step 7: 5274 + 879 = 6153
Step 8: 6153 + 879 = 7032
Step 9: 7032 + 879 = 7911
Step 10: 7911 + 879 = 8790
Step 11: 8790 + 879 = 9669
Step 12: 9669 + 879 = 10548
Step 13: 10548 + 879 = 11427
Step 14: 11427 + 879 = 12306
Step 15: 12306 + 879 = 13185
Step 16: 13185 + 879 = 14064
Step 17: 14064 + 879 = 14943
Step 18: 14943 + 879 = 15822
Step 19: 15822 + 879 = 16701
Step 20: 16701 + 879 = 17580
Step 21: 17580 + 879 = 18459
Step 22: 18459 + 879 = 19338
Step 23: 19338 + 879 = 20217
Step 24: 20217 + 879 = 21096
Step 25: 21096 + 879 = 21975

So, 879*25 = 21975