Please someone should help me explain the code below cos I don't understand how the result is 9

Question

var X=3
X=++X+X++
alert(X);

And the Answer is 9

Answer 1

x = 3

x=++x (x was 3, x is now 4) + x++ (x was 4, x is now 5)
4+5=9

note:
the ++x/x++ operation changes the variable it's not the same as x+1

Answer 2

Thanks