When you multiply two integers, or in fact any two numbers, you are finding the product of those two numbers;
So finding the product is done through multiplication.
There are 5^5 students on the school and 5^2 students per class.
So, think:
1 class ----------- 5^2 students
x classes ---------- 5^5 students
Multiply:
1 . 5^5 = x . 5^2
So,
5^5 = x.5^2
x = 
x = 
x = 
x = 125
There are 125 classes.
The highest amount it could be is 2,499 + 899= 3,898 which could be rounded to 3,900