Is there a way in javascript/jQuery to take two variables with values 60px and 40px and add them together to get 100px?

Or in a more general sense, I'm trying to calculate positions of objects relative to other objects and it would be really convenient if I could do something like this:

$('#object2').css('left', $('#object1').css('left')+'60px');

Of course, that just gives in invalid 40px60px.