let x = 3;
let y = 6;

x += y; // x = x + y
console.log(`x: ${x}, y: ${y}`); // x: 9, y: 6

x -= y; // x = x - y
console.log(`x: ${x}, y: ${y}`); // x: 3, y: 6

x *= y; // x = x * y
console.log(`x: ${x}, y: ${y}`); // x: 18, y: 6

x /= y; // x = x / y
console.log(`x: ${x}, y: ${y}`); // x: 3, y: 6