How would I center a GUI button?

Unity Engine
1

I tried to do this but it wasnt centered…

(GUI.Button (Rect (Screen.width/1.5,Screen.height/1.5,100,50), "Start!")
2

Try this:

var buttonWidth = 100;
var buttonHeight = 50;

function OnGUI(){
	GUI.Button(Rect((Screen.width - buttonWidth)/2, (Screen.height - buttonHeight)/2, buttonWidth, buttonHeight), "Start!");
}