Q1)
1- a*b%3 = 5*9%3 = 45%3 = 0
2- b/a*c-b%a = 9/5*15.0 - 9%5  
             = 1*15.0 - 4  
             = 15.0 - 4 
             = 11.0
3- (b>=a || c==0) && a*b<40
 = (true|| false) && false
 = true && false 
 = false
4- !(1+2*a==3)&&(b-23+a!=1)
 = !(false)&& true
 = true && true 
 = true  
5- z= !((!x&&!y)||y)
   z= !((false&&true)||false)
   z= !(false||false)
   z= !(false)
   z= true

Q2)

float num1, num2;
char op = '+';
switch(op)
{
  case '+': System.out.println(" = "+num1+num2); break;
  case '-': System.out.println(" = "+num1-num2); break;
  case '*': System.out.println(" = "+num1*num2); break;
  case '/': System.out.println(" = "+num1/num2);
}


Q3)

public class Statistics
{
  public static void main(String [] args)
  {
    int x1 = 12, x2 = 20, x3 = 9, x4 = 15, x5 = 10;
    double m , v, s;
    
    m = (x1+x2+x3+x4+x5)/5.0;
    v = (Math.pow(x1-m,2) + Math.pow(x2-m,2) + Math.pow(x3-m,2)+
        Math.pow(x4-m,2) + Math.pow(x5-m,2))/4.0;
    s = Math.sqrt(v);
  }
}


Math.pow(x,2)  = x^2     x*x

((x1-m)*(x1-m) + (x2-m)*(x2-m) + (x3-m)*(x3-m) + (x4-m)*(x4-m)+
(x5-m)*(x5-m))/4.0;


Q4)
1-  int x = -1;
2-  String name = "Ahmad";
3-  double x = 10.5, y = 0, z = 11.5;

4- correct
5- incorrect   begins with a digit
6- incorrect   variable name is a Java Keyword



Q5)

rem = x%y;

div = a/b;

rem

Output:
quotient = 2
remainder = 1
division = 4.5