定宽+自适应布局

　1.float：left+overflow：hidden

.left{
    float:left;
    width:200px;
    margin-right:20px;
    height:500px;
    background:blue;
    }
.right{
    overflow:hidden;
    height:500px;
    background:gray;
        }

2.table

.parent{
    display:table;
    width:100%;
    height:500px;
}
.left,.right{
    display:table-cell;
    background:red;
    color:#fff;
    font:50px '    Microsoft YaHei';
}
.left{
    width:0.1%;
    padding-right:20px;
    background:blue;
}

3.flex

.parent{
    display:flex;
    height:500px;
}
.left{
    width:200px;
    margin-right:20px;
    background:gray;
}
.right{
    flex:1;
    background:blue;
}