unexpected token in ongui function

Hello there an error is my script saying that there is an unexpected token.
The unexpected token is on de last line and starts at the T of ToString.
I cant seem to find out how is should fix it.

 function OnGUI(){
        GUI.Box(Rect(Screen.width*0.22,Screen.height*0.28,200,25), Score.score.ToString());
    GUI.Box(Rect(Screen.width*0.15,Screen.height*0.35,125,25), ("Ringen Opgepakt"));
    GUI.Box(Rect(Screen.width*0.3,Screen.height*0.35,50,25),PickUp.totaalRingen.ToString());
    GUI.Box(Rect(Screen.width*0.375,Screen.height*0.35,100,25), ("x10 pt"));
    GUI.Box(Rect(Screen.width*0.5,Screen.height*0.35,50,25),PickUp.totaalRingen*10.ToString());

On the last line, due to the rules of the language syntax, you are effectively trying to multiply a string by a number, which isn’t possible.

Pickup.totaalRingen is a number

10 is a number

Pickup.totaalRingen * 10 is a number * another number

10.ToString() is a function called on a number that results in a string

Pickup.totaalRingen * 10.ToString() is a number * a string

Use brackets to make Pickup.totaalRingen * 10 an expression on its own, then call .ToString() on the result of that expression:

(Pickup.totaalRingen * 10).ToString()