line-height: 150%; assigns 150% of the font-size to line-height.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Set text indent to 37%</title>
<style type="text/css">
p {
text-indent: 37%;
line-height: 150%;
}
</style>
</head>
<body>
<p>
This is test. This is test. This is test. This is test. This is test.
This is test. This is test. This is test. This is test. This is test.
This is test. This is test. This is test. This is test. This is test.
</p>
</body>
</html>