how do you printin the sum of variables

Answer 1

use print function and add them either inside the function or out.
System.out.println (a+b);

Answer 2

System.out.println(x+y);
where x and y are your variables

Answer 3

Make sure that the two variables you want to add are Integers.
if not use: Integer.parseInt(strVar)

If both variables are Integers then do
System.out.println(a+b)

Answer 4

int x = 5;
int y = 10;

System.out.println(x + y);

/*or*/

int x,y,z;

x = 5;
y=4;
z=6;

System.put.println(x + y + z);