HTML resize image

<!DOCTYPE html>
<html>
<head>
<style>
div {
    width: 420px;
    padding: 10px;
    border: 5px solid gray;
    margin: 0;
}
</style>
</head>
<body>

<h2>Calculate the total width:</h2>

<img src="http://i.imgur.com/6JWdq7v.png" width="450" alt="artweave">
<div>The actual picture is 600px wide reduced to 450px.</div>

</body>
</html>