SOURCE

<div class="wrapper">
	<span class="span1">x123x</span>
	<span class="span2">xkasx</span>
	<span class="span3">xgggjjkox</span>
</div>

.wrapper{
	background: pink;
	height: 200px;
	width: 450px;
	line-height: 200px;
}

span{
	background-color: yellow;
}

.span1 {
	font-size: 12px;
}

.span2 {
	font-size: 24px;
}

.span3 {
	font-size: 36px;
}