请问实现的对吗4-3 4-4 4-5编程

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>

    //4-3编程
    //乘法函数

    var multiply=new Function('num1','num2','return num1*num2;');

    //除法函数
    var divide=new Function('num1','num2','return num1/num2;');

    //加法函数
    var add=new Function('num1','num2','return num1+num2;');

    //减法函数
    var subtract=new Function('num1','num2','return num1-num2;');

    //计算21*32+24/3-5的值
    var box=new Function('num1','num2','num3','num4','num5','return num1*num2+num3/num4-num5;');
    console.log(box(21,32,24,3,5));





//4-4编程

//加法
 function add(num1,num2){
     return num1+num2;
 }
 //减法
 function  subtract(num1,num2){
     return num1-num2;
 }
 document.write(subtract(add(21,32),24));


 //4-5编程


    //加法
    var add=function(num1,num2){
        return num1+num2;
    };
    //减法
    var subtract=function(num1,num2){
        return num1-num2;
    };
    //乘法
    var multiply=function(num1,num2){
        return num1*num2;
    };
    //计算21-32+24*5的值
    document.write(add(subtract(21,32),multiply(24,5)));//109




</script>
</body>
</html>