A simpler way to write the calculator class in OOP PHP

I have created a class called Calculator with the add, subtract, multiply and divide function. The calculator is limited to adding two numbers and returning the result. I am relatively new to OOP,would like to get some input on the class, did i take the long route and if i did is there another way to simplify the class.

Here is the code:

class Calculator {
    private $_val1 , $_val2;

    public function __construct($val1, $val2){
        $this->_val1 = $val1;
        $this->_val2 = $val2;
    }

    public function add(){
        return $this->_val1 + $this->_val2;
    }

    public function subtract(){
        return $this->_val1 - $this->_val2;
    }

    public function multiply (){
        return $this->_val1 * $this->_val2;
    }

    public function divide () {
        return $this->_val1 / $this->_val2;
    }
}

$calc = new Calculator(3,4);
echo "<p>3 + 4 = ".$calc->add(). "</p>";

$calc = new Calculator (15,12);
echo "<p>15 - 12 = ".$calc->subtract(). "</p>";

$calc = new Calculator (20,2);
echo "<p> 20 * 2 = ".$calc->multiply(). "</p>";

$calc = new Calculator (20,2);
echo "<p> 20 / 2 = ".$calc ->divide(). "</p>";