Let's get this math done. We have 879 and we're going to multiply it by 10. This is the same as taking 879 and adding it to itself 10 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

So, 879*10 = 8790