division sets up everything in groups so when you divide 25 by 5 you get 5 groups of 5 so if you are subtracting 5 from 25 you will have to subtract5 5times.
25-5=20 one group of 5 can fit into 25
20-5=15 two groups of 5 can fit into 25
15-5=10 3 groups of 5 can fit into 25
10-5=5 four groups of 5 can fit into 25
5-5=0 so in total 5 groups of five can fit into 25