I have set that if the Input checkbox is checked the opacity turn from 0.5 to 1.

It'not working, it actually works if i do the opposite, but this is not my goal!

My CSS code

    .opacitychange {opacity: 1;}
    #total {opacity: 0.5}

and

    if($("#iva").is(':checked'))
    {
        $('#total').html('+' + vat);
        total += vat;
        $('#total').addClass("opacitychange");
    }    
    else
        $('#total').html('0.00').removeClass("opacitychange");

    if($("#irpef").is(':checked'))
    {
        $('#total1').html('-' + irpf);
        total -= irpf;
        $('#total1').addClass("opacitychange");
    }
    else
        $('#total1').html('0.00').removeClass("opacitychange");
        $("#total2").html(total.toFixed(2));
    };

What's wrong?

Here the case