<!DOCTYPE html>
<html>
<head>
 
<style> 

div{background-color:#CEF279;} 
#tree{width:300px; height: 300px;}  
#tree > img{width: 300px; height: 200px;}  

#tree2 {width:auto;height:auto;} 
#tree2 > img{width: 300px; height: 200px;} 

#tree3{} 
#tree3 > img{width: 20%; height: 20%;}
</style>
</head>
<body>

<h3>div height: 300px, img height:200px</h3>
<div id="tree">
 <img src="tree.png">
</div> 
<h3>div height: auto, img height:200px</h3>
<div id="tree2">
 <img src="tree.png">
</div>
 <h3>div height: 설정하지 않음, img height:20%</h3>
<div id="tree3">
 <img src="tree.png">
</div>

</body>
</html>