Could someone explain me how this code works line to line? Thanks.

Question

var X=10;
var x=7;
var c=5;
var z=(x*x)-(x);
document.write(X-x);
document.write(z);

Answer 1

z= 7*7-7
= 42

X-x= 10-7
=3

Answer 2

X is set to 10
x is set to 7
c is set to 5. // unused var
z is set to x*x-x ==> 7*7-7 ==> 42
prints X-x ==> 10-7 ==> 3
prints z ==> 42