左边固定右边自适应

方法一：flex布局

<div class="wrapper">
        <div class="left">左边</div>
        <div class="right">右边</div>
    </div>

.wrapper {
             400px;
            height: 400px;
            display: flex;
            background-color: blue;
        }
        .left {
            flex: 1;
            background-color: red;
            height: 200px;
        }
        .right {
            float: right;
             200px;
            height: 200px;
            background-color: green;
        }
或者：

.wrapper {
400px;
height: 400px;
display: flex;
background-color: blue;
}
.left {
flex: 1;
padding-right: 200px;
background-color: red;
height: 200px;
}
.right {
200px;
height: 200px;
background-color: green;
}

方式二：display:table-cell的应用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .wrapper {
            display: table;
             400px;
        }
        .left {
            display: table-cell;
             1000px;
            background-color: green;
        }
        .right {
            background-color: yellow;
             100px;
            height: 150px;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <div class="left">左边</div>
        <div class="right">右边</div>
    </div>
</body>
</html>
注意：左侧div必须设置超过父元素减去右侧元素的宽度

方式三：应用float和margin

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>左边固定右边自适应</title>
    <style>
        .wrapper {
             400px;
        }
        .left {
            height: 100px;
            margin-right: 200px;
            background-color: red;
        }
        .right {
            height: 100px;
             200px;
            float: right;
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <div class="right">右边</div>
        <div class="left">左边</div>
    </div>
</body>
</html>
注意：书写代码的时候，right代码在前面