Why does this print "76"?

Question

From a JS Challenge, the following code
var x = 7 + "2";
var y = 4 - "8";
alert(x-y);
alerted "76". Can someone explain why?

Answer 1

var x =7 +"2" wihich gives 72
var y = 4 - "8" which gives -4
in the first line the 7 and 2 are concatenated
but in secon line the "-" sign doesn't concatenate the two values so it converts "8" to int..
and yields -4

Answer 2

thanks! that's a nice way to show when they concatenate or not!