[SOLVED] Decerementing a number

[YourNameHere]

I am having trouble decrementing a number. here is my code:

 

(Using jQuery)

 

function subtract()
{
var pointsLeft = 35;
pointsLeft =-- 1;
$('#points').html(pointsLeft);
}

 

It's been a while since I used this operation so I am not sure what am I doing wrong?