JS 100元购物卡，牙刷5元，香皂2元、洗发水15元 100元正好花完有多少种可能

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
    </head>
    <body>
    </body>
</html>
<script type="text/javascript">
    var c = 0
    var biao = 0
    for(var x = 0;x <=20;x++){
        for(var y = 0;y<=50;y++){
            for(var z = 0;z<7;z++){
                c++;
                if(5*x + 2*y + 15*z == 100){
                    biao++;
                }
            }
        }
    }
    alert(biao)
</script>