What is the remainder after dividing 13 by 5?
3
You may recall how in grade school you did division like this:
13 / 5  ==  2 with a remainder of 3.
This is because 13 == 2*5 + 3.
The symbol for finding the remainder is % (percent sign).
This symbol is also called the modulo operator. 
If you look in the 
 table of operators
you will see that it has the same precedence as / and *.
Here is a program that is worth study:
class RemainderExample
{
  public static void main ( String[] args )
  {
    int quotient, remainder;
    quotient  =  17 / 3;
    remainder =  17 % 3;
    
    System.out.println("The quotient : " + quotient );
    System.out.println("The remainder: " + remainder );
    System.out.println("The original : " + 
        (quotient*3 + remainder) );
  }
}
Copy this program to a file and play with it. Change the 17 and 3 to other numbers and observe the result.
Why were the innermost set of parentheses used in the statement:
    System.out.println("The original : " + 
        (quotient*3 + remainder) );