what is the matter my java script : Its not working

what is the problem

i am trying put return values  but browser not display anything  :(

please help me 

i newbie  so please help me 

    <html>
    <head></head>
    <body>
    
    <script type="text/javascript">
    
    function (){
    document.write(100+50);
    }
    
    function 2(){
    document.write(100-50);
    }
    
    function 3(){
    document.write(100/50);
    }
    
    function show(){
    1();
    2();
    2();
    }
    
    show();
    
    </script>
    
    </body>
    </html>